It's running super rich though and is burning through gas like crazy, so I don't believe it's getting starved of fuel
Out of curiosity, have you checked the fuel injectors? Could it be possible that one or more are dumping lots of fuel on acceleration causing the cylinder(s) to drowned out? How's your air filter?
I'm not sure if reading the spark plugs on a fuel injected engine is similar to that on a carburetted engine but if so, I'd take it for a vigorous run and then check the plugs. Are they sooty? If so, sounds like too much fuel or not enough air. When I rebuilt the cars on my KZ650, I had a high speed stumble and then it would smooth out and accelerate. It used a lot of fuel - way more than it should. Reading the plugs showed that the a couple of cylinders were running way too rich and that meant fiddling with the main jet and the carb needles to get rid of the problem.
(BTW, on my KZ650, when I removed the air filter element, it lets more air in making the mixture leaner making the problem better but not solving it.)
------------------ Mike in Sydney
[This message has been edited by Mike in Sydney (edited 04-05-2020).]
Originally posted by Mike in Sydney: Out of curiosity. have you checked the fuel injectors? Could it be possible that one or more are dumping lots of fuel on acceleration causing the cylinder(s) to drowned out?
I'm not sure if reading the spark plugs on a fuel injected engine is similar to that on a carburetted engine but if so I'd take it for a run and check the plugs. Are they sooty? If so, sounds like too much fuel or not enough air. When I rebuilt the cars on my KZ650, I had a high speed stumble and then it would smooth out and accelerate. It used a lot of fuel - way more than it should. Reading the plugs showed that the a couple of cylinders were running way too rich and that meant fiddling with the main jet and the cab needles to get rid of the problem.
I have not checked the injectors yet that was going to be my tomorrow project 😂 and my plugs and wires are all brand new so no issues there, and I made sure they are working correctly. And the issue is through full acceleration it's choppy and slow and then it'll have a push you back in your seat moment and then it'll get choppy again.
I'd pull the plugs on the trunk side and see if they are fouled with soot. If they are then, it may be a fuel injection issue.
I'm 90% certain it's water, and I'll check those and the injectors tomorrow and let you guys know what I find, also I really appreciate the help with this, wouldn't be able to do it on my own😂
I can check fuel pump, I already did fuel filter and it is running rich and burning through gas so idk If it would have an issue with that?
Checking fuel pressure isn't just done while the engine is running. After the engine is turned off, the fuel pressure should remain stable for quite awhile before it slowly drops. If it drops immediately, you'll know you have leaky injectors or some other related issue.
If it's water, chances are it's condensation . Does it happen every time the car is started or only after it's been sitting for a while and the car is cold? If it happens every time the car is started whether hot or cold then it could be serious. If only when it's cold, I'd guess it is condensation from the atmosphere
If it's water, chances are it's condensation . Does it happen every time the car is started or only after it's been sitting for a while and the car is cold? If it happens every time the car is started whether hot or cold then it could be serious. If only when it's cold, I'd guess it is condensation from the atmosphere
I'm not sure what looking at them is going to tell us.
Did you do the fuel pressure leak down test before you pulled them?
I thought I would pull them out first and make sure they didn't look like garbage since I've seen some preety bad ones that are stock that look super bad so I thought I'd check with that
While you have them out, check the resistance of each injector since they're now easily accessible. Maybe also use a battery to make sure each one "clicks". Details on doing this can be found online.
[This message has been edited by Patrick (edited 04-08-2020).]
I did not mention fuel pump because it is on your list of stuff you have already replaced. But the symptoms you just described sound a lot like a fuel pump going bad. So if you have not replaced the pump you might want to look there.
The water coming out the tailpipe is just vapour that condenses back in to water until the exhaust piping and muffler warm up. The black splatter marks are the water washing the carbon off the inside of the tailpipe. All fuel injected cars do this, newer cars just do not produce the black splatter marks as much.
------------------ 86 GT built 2.2 ecotec turbo rear SLA suspension QA1 coilovers on tube arms
I did not mention fuel pump because it is on your list of stuff you have already replaced. But the symptoms you just described sound a lot like a fuel pump going bad. So if you have not replaced the pump you might want to look there.
The water coming out the tailpipe is just vapour that condenses back in to water until the exhaust piping and muffler warm up. The black splatter marks are the water washing the carbon off the inside of the tailpipe. All fuel injected cars do this, newer cars just do not produce the black splatter marks as much.
Good to know it just seemed like quite a bit Coming out of it so just had me worried was all.
While you have them out, check the resistance of each injector since they're now easily accessible. Maybe also use a battery to make sure each one "clicks". Details on doing this can be found online.
Checked them for resistance and for clicking good in both categories.
Alright bois I do believe I am just going to take it to a shop to have them tell me what the issue is and then I will fix it from there, its been months trying to fix this issue with no luck so far and my hairs turning gray from it, I appreciate all the help and I will let you guys know what they say it is.
Fuel pressure at idle is 40 and when I push the throttle down it drops to 31ish?
That is the normal operating range of the fuel pump. After you have the 'experts' look at it, do us a favor and post what you find out. It would still be nice to know what happens to the fuel pressure when you turn the engine off.
[This message has been edited by Gall757 (edited 04-11-2020).]
no. No connection between engine speed and fuel pump speed. Do you have the resistance readings on your injectors for Olejoedad?
I thought as engine speed went up demand for fuel increased? And off the top of my head I think they were all around 12ohms, let me see if I can find the exact readings but I know I looked it up after testing and they were all within range.
I thought as engine speed went up demand for fuel increased?
Of coarse it does.
The fuel pump pressurizes the system and the fuel regulator determines how much fuel goes to the injectors and how much goes back to the fuel tank, based on a change in vacuum pressure. The usual spec for the 2.8 V6 is around 42 lbs of pressure with the engine off, and 32 with the engine running. If you were at 25 lbs you may have a problem, but not 31.
The fuel pump pressurizes the system and the fuel regulator determines how much fuel goes to the injectors and how much goes back to the fuel tank, based on a change in vacuum pressure. The usual spec for the 2.8 V6 is around 42 lbs of pressure with the engine off, and 32 with the engine running. If you were at 25 lbs you may have a problem, but not 31.
From other posts I've read and other searching I saw that usually pressure tends to rise not drop when under load? Just trying to wrap my head around it is all, I appreciate you taking the time to explain this all.
The Fiero is not that smart. I suppose newer cars have a computer connection to the fuel pump that dictates delivery speed....but not the Fiero. The system works pretty well for how primitive it is.
Edit: and what else is one going to do during a Saturday Afternoon 'stay at home' order?
[This message has been edited by Gall757 (edited 04-11-2020).]
The Fiero is not that smart. I suppose newer cars have a computer connection to the fuel pump that dictates delivery speed....but not the Fiero. The system works pretty well for how primitive it is.
Edit: and what else is one going to do during a Saturday Afternoon 'stay at home' order?
LOL you're right I'd just much rather be enjoying the car rather than fixing it, what can ya do 😂 so what are you thinking might be the issue then? Any other info I can give to help out?
1. Do the fuel pressure test that Patrick asked for. 2. Get the resistance numbers that Olejoedad asked for.
These guys want to help Fiero owners, but they can't do much with no information.
If the injectors are still out of the car....clean them or get them cleaned by a service. They are most likely good and should not be replaced because they are probably better than new ones. There are tutorials on line if you want to clean them yourself.
I thought my response had posted , but the fuel pressure leak down test that patrick said to do I did when testing the fuel pressure and upon turning off the engine and letting it sit for three minutes the pressure didn't drop at all if any maybe one psi, for the fuel injectors I got a cleaning kit from the local parts store and cleaned them and reinstalled them as when I did the resistance test and looked up what they needed to be at they fell within range , also did battery test and they all clicked. Also not trying to upset anyone with my lack of knowledge and I really appreciate the help. I don't have the exact readings but I know for sure they were good, I can re-pull them out and post the exact ones if necessary.
Just to sort of update the thread took it to the shop in town and map sensor was bad .....woooooooo, and apparently two injectors were bad , 1 and 3 so with new map sensor car actually accelerates still a little choppy but so much better , going to be getting some injectors from a lovely fellow on here and hopefully should be all good. Thanks for the help everyone sorry if I was a nuisance I really appreciate the help I got from everyone, I will let everyone know how the car goes after the swapped injectors.
