I have a 2.8L stock engine. Whenever I start it up cold, the rpms go upwards of 2,000(from what I hear that's normal). But when I try to drive on a cold engine, it boggs down and seems like it wants to die. I give it more gas, and not much happens for a few seconds and then it starts going like normal with getting on the gas. When the engine has warmed up, everything is perfectly fine. It's had performance exhaust manifolds, new muffler, new alternator, starter, battery and some other minor stuff. It doesn't bother me that I have to wait a few minutes to drive, but was just looking to see if anybody had the same issue or knows what's going on. Thanks for any information
Define cold........ Are you talking about a winter day with cold air temps.....or are you talking about a summer day but it is the first run of the engine and the engine is cold? There are several possibilities as to why the engine bogs down until it warms up..... 1. Here is one that most people don't think about......a carb. can ice up even with an outside air temp. in the 90's....when the air temp. and the dew point get close enough to each other.....carb. ice occurs. I would have to go look at my engine to see how warm air is introduced,I don't remember off the top of my head......but,you may not be giving your engine enough time to heat the exhaust up and provide warm air to the intake system to prevent ice from forming...after a few minutes enough heat has built up and it drives fine. 2. Possibly you have a mixture issue.....
The initial high rpm after start up serves a couple of purposes...... 1. To build oil pressure quickly to lube the bearings 2. To heat the exhaust up quickly for the intake system to prevent ice 3. To heat the cylinders quickly for proper expansion of piston and rings so that oil consumption is minimized,plug fouling is minimized and compression is built up fast by the piston and rings expanding and sealing against the cylinder walls.
[This message has been edited by MadProfessor8138 (edited 04-10-2016).]
Cold as in the first start of the day. It does this no matter what temperature it is. also, why would I have to do anything with a carb? Fieros are fuel injected?
Throttle body is not a true fuel injection system and will suffer from carb ice..... Even fuel injection systems have been known to ice up on occasions,that's why there is heat supplied no matter what type of fuel delivery system is used....either from the exhaust or from the cooling system on different engines in general.
I would have to go look at my engine to see how warm air is introduced,I don't remember off the top of my head......but,you may not be giving your engine enough time to heat the exhaust up and provide warm air to the intake system to prevent ice from forming...after a few minutes enough heat has built up and it drives fine.
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Originally posted by MadProfessor8138:
Throttle body is not a true fuel injection system
Are you confusing the OP's 2.8 with an '84-'86 duke?
There is no warmed air from the exhaust being supplied to the intake of a V6 Fiero for "cold" starts. And I have no idea why you would state that the fuel system on a Fiero 2.8 is "not a true fuel injection system".
I have a 2.8L stock engine. Whenever I start it up cold, the rpms go upwards of 2,000(from what I hear that's normal). But when I try to drive on a cold engine, it boggs down and seems like it wants to die. I give it more gas, and not much happens for a few seconds and then it starts going like normal with getting on the gas.
It would be helpful to know what tranny you have , but I suspect you have an automatic... which would make the issue you're experiencing that much more noticeable. What you've described is not normal for a healthy engine.
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Originally posted by 0WNINGD3ATH:
When the engine has warmed up, everything is perfectly fine.
I don't know what your experience is with Fieros, and/or what you might consider "fine". It's possible that even when your engine is warmed up and appears to be running "perfectly fine" that it's still somewhat sub-standard. I've had one automatic V6 Fiero ('86 GT), and it had no issues or lack of power when the engine was cold, even in the dead of winter.
When's the last time you've changed the spark plugs, or plug wires, checked the ignition timing, checked your fuel pressure, etc? It's difficult to suggest specific things without knowing what type of regular maintenance has been taking place.
[This message has been edited by Patrick (edited 04-11-2016).]
A throttle body is not a true fuel injected system....it is basically a high tech carb in its operation. Fuel and air are mixed together through the throttle body and therefore it is capable of suffering from (carb)ice. If you don't believe me,I have a 89 GMC truck with a throttle body that will ice up constantly if I pull the heat riser tube off of the exhaust/breather . A true fuel injection system utilizes injectors and a air intake that are separate from each other....and therefore reduces the chances of ice occurring,but it is still not foolproof....ice can still occur in the intake due to humidity in the air that is being ingested. If you're a pilot,like myself,you are well aware of carb icing and the use of carb heat.....lol
Well,by pure coincidence I happen to own 1 of them and 2 4.9 cars Patrick.... And as I originally stated,I would have to go pop the deck on one of them to see if they use a heat riser of some sort....never really paid attention to that detail before....but ,we have been blessed with enough rain to make Noah envious this past week and I haven't felt the need to get soaked so I figured someone else would be able to answer that question.
Not really sure where you've obtained your knowledge pertaining to fuel systems so I will help you out.....a fuel system is either carbed,throttle bodied or fuel injected. A throttle body is not a pure fuel injection system. It uses the principals of a carb and tweaks it a little by eliminating the float bowl, metering needles and jets....instead,it uses pressure from the pump and injectors housed inside of the throttle body to operate. A pure fuel injection system separates the fuel injection and the air intake....this greatly reduces the risk of ice but it is still possible for the air intake to form ice due to the Venturi effect and humidity in the air. Class dismissed.....
And why you assume that my assertions to the OP's question is out in left field is beyond me..... Just because the 2.8 uses a throttle body does not eliminate the possibility of ice. Once again...a throttle body is just a high tech carb....and carbs are subseptible to.....WAIT FOR IT.............CARB ICE !!!! So the comment that the OP could be experiencing icing is not out in left field. I only stated that being a pilot,I am well versed that carb ice is real,happens even on the warmest of days and it tends to turn my air conditioner off when it happen.....the a/c would be that big thing that goes round and round on the front of my planes. Turn it off and watch me start sweating......
Sorry,I didn't mean to hijack the thread but there was a need for a quick education......
[This message has been edited by MadProfessor8138 (edited 04-11-2016).]
Actually madproffessor, it is out of my book. This problem doesn't just occur in low temps, as I stated before. It's currently in the low 90's and it still happens... Please stop hijacking this thread. I don't care what you have to say at this point because I know there is other people like the one you're arguing with and theogre who know 10 times more about Fieros than you. I'd much appreciate their opinions over a person who bitches with somebody rather than collaborating to come to a conclusion.
Wasn't meaning to start a ***** fest.....and if it appears that way I apologize,it was not my intent. Was only offering one possible explanation as to the rough running situation that you were experiencing....it's still a valid point to consider. I would have to go pop the deck lid on my car to tell you where the fuel lines run...if it is a true fuel injected setup and not a throttle body I sincerely apologize to you Patrick,but there seems to be a load of 2.8 throttle bodies for sale on the net for the Fiero though.
However,when I offered an opinion as to the OP's original question you had no need to insult my intelligence by projecting the opinion that I don't own a Fiero and I've never worked on one....I stated that I couldn't recall from memory the setup of the engine and would have to go look. Thanks for posting a pic Patrick,that helps refresh my memory. That sure looks like a throttle body setup to me..and there's a bunch of 2.8 throttle bodies for sale on the net. I could be wrong though...it might be a true fuel injection setup,hard to tell from the pic. Out of curiosity,what is the tube coming off the bottom of the EGR valve?.....is that possibly a heat riser setup? If it is a heat riser tube...that is probably where your warm air is being introduced to the intake system to prevent icing.
Once again OWNINGD3ATH,I apologize for the curt post....was only trying to help you solve a problem.
[This message has been edited by MadProfessor8138 (edited 04-11-2016).]
...if it is a true fuel injected setup and not a throttle body I sincerely apologize to you Patrick...
I'm not looking for any apology. I'm just trying to help eliminate incorrect information being offered to the OP. Both myself and Gall have tried to tell you that you are mistaken, but for whatever reason you continue to dismiss what we say.
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Originally posted by MadProfessor8138:
I could be wrong though...it might be a true fuel injection setup,hard to tell from the pic. Out of curiosity,what is the tube coming off the bottom of the EGR valve?.....is that possibly a heat riser setup? If it is a heat riser tube...that is probably where your warm air is being introduced to the intake system to prevent icing.
The tube coming out of the bottom of the EGR valve is... get ready now... the EGR tube!
Again, you refuse to acknowledge that anyone else might know what they're talking about. I've already told you that there's no heat riser setup on a Fiero 2.8 engine.
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Originally posted by Patrick:
Are you confusing the OP's 2.8 with an '84-'86 duke?
There is no warmed air from the exhaust being supplied to the intake of a V6 Fiero for "cold" starts. And I have no idea why you would state that the fuel system on a Fiero 2.8 is "not a true fuel injection system".
You are correct sir.....I stand corrected. I just went and popped the deck lid on my car....it is using a MPFI setup. Whether you want an apology or not....you got one....so take it....lol
That is why we are all on the forum....to learn something we don't already know. I learned something with your help and by looking at my engine. That is one weird looking EGR tube......didn't think to look at mine when I opened it up......it's still pouring rain here so I was in a hurry. I have seen a setup like that in the past.....vacuum line on top,EGR draws gases up from the bottom mounting and then it is passed back to the engine through the EGR tube....which adds heat to the system. Must operate differently on the 2.8 from what you describe.
Anyways,my apologies sir.........possibly a kiwi for admitting that I was wrong? Lol
That is one weird looking EGR tube...... I have seen a setup like that in the past.....vacuum line on top,EGR draws gases up from the bottom mounting and then it is passed back to the engine through the EGR tube....which adds heat to the system. Must operate differently on the 2.8 from what you describe.
Oh, I'm sure the EGR system eventually adds heat to the intake... but from what I understand, the EGR valve doesn't even open on the Fiero 2.8 until after the engine reaches a certain temperature (and only under certain driving conditions). So I think it's safe to say that the EGR system on this engine has nothing to do with warming up the engine from a "cold" start.
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Originally posted by MadProfessor8138:
You are correct sir.....I stand corrected. I just went and popped the deck lid on my car....it is using a MPFI setup. Whether you want an apology or not....you got one....so take it....lol
A throttle body is just that, a body that has a throttle plate or plates in it; port injection systems use at least one throttle body to control the amount of air going ino the engine. Throttle Body Injection or TBI has a throttle plate(s), plus it also has the injectors located in the throttle body, hence the name.
So yes, you can buy throttle bodies for a port injected engine and for a TBI engine but they're quite different.
Actually madproffessor, it is out of my book. This problem doesn't just occur in low temps, as I stated before. It's currently in the low 90's and it still happens.
From what you're describing, it sounds like the engine is running lean initially, possibly from a vacuum leak or even EGR valve leak.
Have you checked your coolant temp sensor to see if it's reading in the right range for the temperature? I had one that did the opposite, ran fine until it got fully up to operating temp then went to an elevated idle and rich mixture.
Honestly, I don't think it's a vacuum leak but I could be wrong. I had this Fiero in a shop for exhaust manifolds (not my choice. They screwed the originals up) and they checked over for any leaks. I currently can't hear any leaks and have had it smoke tested by a friend and didn't have any at the time. When I get my new plugs/wires I'll go buy a new coolant temp sensor and see if that helps. Thanks for the suggestion mender!
My V6 cold idles at about 1500 rpm. It is possible that a cracked EGR tube actually leaks when cold, but as it gets warmer the crack is sealed. Warm idle should be around 950 rpm,
I would start with small cheap things like you are doing, then work your way up to the harder things. It sounds like its not running well in open loop. The number of sensors used in open loop aren't very many, but coolant temp is one of them, I believe.
It shouldn't be an EGR leak. The car had a massive hole in the EGR tube when I bought it, so I jumped to the fierostore and bought/installed the new one. When I get the intake manifold off and do some replacing of sensors and various other parts later this week, I'll make sure that the EGR and everything else isn't leaking and is properly tightened. Also, is there a sensor or something that is able to change the idle? because the shop I had it at when they were changing the manifolds said something about adjusting the idle. Currently, when the engine is cold, the initial start up is around 15-1700 rpms, and after about 5 minutes it'll drop to around 1,000.
[This message has been edited by 0WNINGD3ATH (edited 04-12-2016).]
Also, is there a sensor or something that is able to change the idle? because the shop I had it at when they were changing the manifolds said something about adjusting the idle. Currently, when the engine is cold, the initial start up is around 15-1700 rpms, and after about 5 minutes it'll drop to around 1,000.
Hopefully the shop didn't screw around with the throttle-plate stop adjustment... which is set and sealed at the factory. The Idle Air Control valve working in conjunction with the ECM is what controls the idle speed.
[This message has been edited by Patrick (edited 04-12-2016).]
Have you checked the fuel pressure? I'm not sure what the actual pressure would be on the 2.8 but there is generally a minimum pressure that injectors need to operate at. Is it possible that you might have a fuel pump that is going bad and it acts up when it is cold,it sticks so to speak....but then frees up after its ran a few minutes and warmed up? It may sound extremely odd but the pump in my Saturn did that very thing....ran fine after replacing the pump.
Is it possible or probable to have an internal leak with the intake on a 2.8? Vacuum leak while it is cold but then seals itself when the engine heats up and expands.... Have you tried checking for vacuum leaks with the engine cold...when you first experience the issue?
[This message has been edited by MadProfessor8138 (edited 04-12-2016).]
I remember back a ways that I took the idle air control valve out to clean it a little bit when I replaced my TPS trying to figure out this same issue. I can't remember for sure, but I think it ran better for a while after I cleaned that up, then went right back to how it is now.
Also, make sure the tube that goes from the back of the throttle body to the intake is seated properly and the rubber part is in good shape.
Just for laughs I decided to see if the 2.8 in my '87 parts car (auto) would start. WIth a little playing it did, and it's acting almost exactly the same as yours! So far have found and fixed a bad distributor, loose intake bolts, and the loose tube on the throttle body. The first got it running and the last two resulted in a noticable improvement but it still has issues. Still am checking things out but I'll let you know if I find something.
[This message has been edited by mender (edited 04-15-2016).]
If your plugs haven't been changed for a long time change them.
If neither of these, get a scan cable and scan the engine while this is happening. Look at the CTS temperature and make sure it looks right. Perhaps the CTS is reporting the engine temp is much warmer than actual. Look at the MAT temperature and make sure that looks right. Again look to see if it shows too warm. If they both look right, see if the trouble goes away when the engine goes into closed loop.
When the engine is first started, the ECM just injects the amount of fuel it is programmed to. This is because the O2 sensor doesn't function until it gets hot. The O2 sensor sits in the exhaust stream. Once the O2 sensor gets hot, the ECM then adjusts the mixture based on the O2 sensor.
Mine has 40 psi that maintains for several minutes after key-off. No problem with that. Just replaced the CTS. Sounds laboured after starting as it runs up to idle. No access to scanner.
[This message has been edited by mender (edited 04-16-2016).]
I'll check the fuel pressure Tuesday for sure. That's when all the parts I got off the fierostore.com come in. I've honestly got no clue how old the plugs are. I bought the car and forgot to ask the person. I ordered the tune up kit which comes with new wires, plugs, distributor cap and rotor. There's a knocking in the engine which I'm 99.5% sure is a loose rocker so while the intake is off I'm going to be replacing the fan control switch, the thermostat(190 degrees), and a coolant temp. switch. Hopefully with all these replacements, I'll be able to run just fine again. I'll for sure keep everybody posted on the results. And thank you to everybody for helping me diagnose this troublesome it really means a lot to me.
Just some update photos. I got the upper/lower intake manifolds off. I took the rear valve cover off as well. Currently, I have replaced the spark plugs, wires, distributor cap & rotor and the thermostat. The plugs were horrible!!! Monday, I'll be cleaning off the intakes and valve cover. Then after they are clean, I'm going to sand the paint off and repaint them bright red. Tired of looking at the dull and faded/chipped red. Everything has gone somewhat smoothly except for the bolt on the valve cover that's under the dog bone. That is a pain in my a$$ to loosen/tighten without taking the dog bone off.
[This message has been edited by 0WNINGD3ATH (edited 04-23-2016).]
That is a pain in my a$$ to loosen/tighten without taking the dog bone off.
Taking the dog bone off is pretty simple and straightforward. In the long run it would probably be a whole lot easier and quicker for you to remove it than to try and work around it. Makes cleaning the area a whole lot easier as well.
[This message has been edited by Patrick (edited 04-23-2016).]
yeah, I think when I start reassembling things, I'm for sure going to take that off because if I don't, I'll have to turn the valve cover bolt like 1/100th of a turn every time lol. That'll get rid of my worries towards probably the hardest part. next point comes when I start putting in the lower intake because of all the lines that are in the way. With some time and very small maneuvers I will have it back in place and torqued down.
next point comes when I start putting in the lower intake because of all the lines that are in the way.
You mean the middle intake? You still have the vacuum lines in the way? This is my Formula a couple years ago before I pulled my middle intake. I like to get all those delicate glass tubes out of the way.
Middle intake or lower intake, same thing. I feel like it's more work trying to find the end to all those little brittle lines and take them off than to just slide the manifold right under them. Plus that's more work putting everything back together. Even though it would make things go a whole lot smoother, the time difference isn't work to me. And the second picture I linked shows my lower intake with all the lines on it still. (just right click and open in new browser to view it)
[This message has been edited by 0WNINGD3ATH (edited 04-24-2016).]
there is three? everywhere I'm looking I only see the bright red upper intake, and the silver v shaped one that the injectors plug into. would you happen to have a photo of the 3rd piece? I'm curious now.
, but I suspect you have an automatic... which would make the issue you're experiencing that much more noticeable. What you've described is not normal for a healthy engine.
