Need help and new here. My 87 2.5 starts and idles good but soon as it is put in ger and gave any throttle it backfires pretty bad through intake. In park it wil rev just fine?? Just put new fuel pump on and it ran great for a day after the install. Next day its running like crap when in gear. Its a auto and i just did compression check which shows 125psi on all 4. New plugs also. No change. Someone please help me?
Yes plug wires are new It will rev in park I meant backfire through intake. Compression was 120 on al 4. Check engine light is on and currently checking codes. Thanks for any qnd all input
New plugs? Exactly what plugs? Bosch +2 and +4 are known problems. DIS hates some "improved" "performance" plugs.
Check but not don't trust the data and think points to exact problem. Iffy coil(s), wire(s), and/or plug(s) can cause this. might be PIM too. See my Cave, DIS Ignition
Bad EGR valve or vacuum line to it can cause this too plus ECM programming expect a working EGR. See my Cave, Emissions
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
Used ac delco plugs New wires New fuel pump New fuel filter Checked all vacum lines It will rev when in park just not in gear as soon as its in gear and gave any gas it backfires through intake. Code say map sensor though i dont think it is that. Keep help coming please.
Originally posted by Chris38: It will rev when in park just not in gear as soon as its in gear and gave any gas it backfires through intake. Code say map sensor though i dont think it is that. Keep help coming please.
Very likely your wrong... Because MAP is "Vacuum Advance" and Boost Retard for All HEI w/ EFI and DIS. (HEI w/ Carb uses mechanical advance.) No MAP = Big problem for ignition.
ECM can give DTC for bad ECM is likely: Bad MAP Bad wiring. Wrong port at the TBI.
Test MAP w/ a hand vac pump w/ gauge. See my Cave, Sensors Quick Ref
Headed to get the map senor now. I have no way to test it so guess i will give it a shot. Wish i could just gut all this electronic stuff and put my progressive weber on. Things would be so much easier.
Well, new map sensor did not fix the problem. It did shut off engine light. Still idlles and revs in park but soon as you put it in drive it backfires through intake with any throttle input. I am clueless now. Pulled valve cover just to inspect and all looks good. Done another compression check all good. Put new ac delco plugs in with new wires. Still no change. Keep in mind this was same problem when we had a bad fuel pump. Put a new one on and it ran brand new for a day. Then the next day it acted as if we hadn't changed it. I hear the pump running so i wouldn't think a w day old delphi pump could have went bad that fast. Please give me some more ideas.
Going back to the fuel pressure. I know it was doing this exact same thing before fuel pump replacement which fixed the problem for one day. That being said i am going to check the fuel pressure whith hopes that the regulator might have went out after new pump install. Most say that low fuel pressure will not cause a backfire through intake but i know first hand the pump replacement DID fix it for a day. I am leaning to this problem being another faulty pump or a failed regulator? Especially since symptoms are exact same as before fuel pump fix(replacement ). It just acts like its not getting fuel under any kind of load. Out of gear its fine. Let me know what you think. Meantime i am testing pressure. Thanks to all.
Fuel pressure was 20psi out of pump. Pulled the regulator and it looks good also. Injector appears to be spraying good. Guess i will now check the coils and ignition control module. Getting really frustrating. Anyone heard of carbing these cars? At this point i am not sure i will ever get it drivable.
Fuel pressure was 20psi out of pump. Pulled the regulator and it looks good also. Injector appears to be spraying good. Guess i will now check the coils and ignition control module. Getting really frustrating. Anyone heard of carbing these cars? At this point i am not sure i will ever get it drivable.
You could take it to a shop and have them look into it. It sounds like you are not familiar with electronics. It may cost a few hundred, but it would be fixed, or you would know the issue. You don't have the tools or knowledge about these cars (which is normal). Back in the day, people needed specific tools and instruction to tune a vehicle. The same is true for modern cars. I have shop manuals and tools to help me diagnose both old and new cars (carb and injection), but I know my limitations and sometimes the vehicle just needs someone with more expertise. Save yourself some grief, and cash... have it looked at by a shop, to at least determine the issue.
Not sure you are correct with my experience on cars and eletronics. Just because i havent had experience on this DIS Junk doesn't mean i can't learn. I do have many tools for test, and have done many on this car. I recently built a 87 porsche 944 turbo from parts including all electronics(500hp). I just know the car sounds great in park and revs perfect, but soon as you put it in drive and give it fuel it will start the backfire issue and does not wanna go. I have tested everything but the ignition components. I just cant see it being ignition related if it idles and revs in park? If we all took our problems to someone to fix we wouldn't learn nothing so i am gonna keep trying a few days. Then mabe to a shop.
Good point. one i haven't thought of. It is a automatic and it is electronic. Just not sure how to test. Seem as if soon as its put in gear the trouble starts. Drive or reverse same results sputtering and popping through intake. At this point i would try anything.
If i knew i could get the auto trans to shift correctly i would convert to a weber and a distributor setup. I got a new weber on the shelf. I converted a vw cabby (cis)last year and its been a dream to drive. Although these dis 2.5 must not be as easy. Haven't found not one person who has done it? Can't see where it would be hard other than the ecm controlled trans? going to check coils, pim and crank sensor first. I can see a sensor making it run rough but this thing goes nutty when you try to drive it. Then put it in park or neutral its smooth as glass. Good greif!
Just done some test i found on the trans. All passed test. TC and third gear switch working. So i do not think it is a trans problem causing the problem. Checking coils and pim tommorw. If anyone on here has done a carb swap please feel free to chime in. Thanks for any and all advice.
Problem Is called "Backfire under load" and is very common on all engines. I've seen this w/ carb and 100% mechanical ignition w/ vacuum advance.
ANYTHING that cause timing change under load... MAP and other sensor problems. ECM or PIM is near death. Just Wiring to ECM can cause sensor or PIM/ICM errors. Worse often w/o setting any DTC. Iffy coil(s) or coolant on them can "short" under load. "Dead" EGR will cause this too as noted above. Example "Bad" Valve can open when exhaust pressure goes high and/or have vacuum problems.
Thanks theogre. I will pull the coils tommorw along with pim to get it tested. Will also look at the egr while im at it. What about the injector itself. It appears to be spraying but i do not see a pulse? I know on my porsche you can hear the pulse. Should i test it? I didn't see any dripping just a constant spraying while at idle.
Originally posted by Chris38: Thanks theogre. I will pull the coils tommorw along with pim to get it tested. Will also look at the egr while im at it. What about the injector itself. It appears to be spraying but i do not see a pulse? I know on my porsche you can hear the pulse. Should i test it? I didn't see any dripping just a constant spraying while at idle.
No "pulse" then the injector will flood and kill the engine. Engine always have an injector pulse except maybe at WOT. MAYBE at full throttle engine can eat fuel but I'm guessing even then will flood the engine w/ injector full on.
Plus you will very likely have DTC 45 for flooding if engine doesn't die first.
For nubes, most times 700 TBI injector at idle sounds same to valve noise. Dukes have valve noise to start w/ because of GM bean counter design.
Get a scan tool may help but It might not in this case. Every sensor etc will show up in ECM's streaming data, even cruise control, for this ECM. example: http://www.reddevilriver.com/aldl.html
Might also try pulling the o2 sensor and taking a quick spin to see if it eliminates the backfire. Could be a clogged cat.
Normally a crank position sensor either works or doesn't. I had a cracked one which caused a stumble and backfire. If you do pull the coils to test probably wouldn't hurt to replace the cps.
Thanks done the cat test this afternoon already. Even hooked a 0 to 10 psi gauge in 02 hole. Was not stopped. I appreciate everyones help very much. And sorry if i have asked too much. I am just trying to learn this system by real people with experience with them.
As far as taking it for a spin? Not gonna happen soon as i place it in drive it gets real bad fast with any throttle input other than just very light. Not even drivable at this point.
Might also try pulling the o2 sensor and taking a quick spin to see if it eliminates the backfire. Could be a clogged cat.
Normally a crank position sensor either works or doesn't. I had a cracked one which caused a stumble and backfire. If you do pull the coils to test probably wouldn't hurt to replace the cps.
Same here, I had a backfire and it turned to be a cracked crank sensor.
Do you have a GM shop manual and/or a scan tool? There are steps to follow within the shop manual, when it comes to backfire/miss under load, etc.
It can be ignition related, because Drive changes the load on the engine. A weak spark can allow it to idle, but die when put into gear. Did you verify that your wires are in the correct position and properly snapped onto the plugs and coil? Are the wires good?
I had an 88 that had a cracked coil and when moisture got in there, it wouldn't run correctly. You can go to a junkyard and buy a coil/ignition module unit pretty cheap as they were used by many GM vehicles at that time.
Will it run in drive if you put more fuel down the TBI? If so, I would look at the fuel delivery. If not, then ignition. That same 88 had a bad injector, and while it looked OK, it really wasn't giving the engine enough fuel.
A scan tool would tell you if the other sensors are reading properly, that is why I mention about taking it to a shop, vs swapping parts, which can be a crap shoot.
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Originally posted by Chris38:
Not sure you are correct with my experience on cars and eletronics. Just because i havent had experience on this DIS Junk doesn't mean i can't learn. I do have many tools for test, and have done many on this car. I recently built a 87 porsche 944 turbo from parts including all electronics(500hp). I just know the car sounds great in park and revs perfect, but soon as you put it in drive and give it fuel it will start the backfire issue and does not wanna go. I have tested everything but the ignition components. I just cant see it being ignition related if it idles and revs in park? If we all took our problems to someone to fix we wouldn't learn nothing so i am gonna keep trying a few days. Then mabe to a shop.
Remove three large bolts and carefully pull the whole brick.
1 big bolt needs thread sealer or likely will leak oil.
Use Brake grease between pim and aluminum "tray" to install Past I said use heatsink grease but area is too big and most formulas doesn't flow any extra out of the space.
Factory install them dry but water and crap can wick in and corrode both faces. A small amount of brake grease keep that out and any extra doesn't attack plastic.
Got the coils and pim off. Pim tested bad at oreilly auto. New pim New coils just to be safe And new crank sensor will be installed tommorw. Also the egr valve was bad. This part was special order so i am going to use a block off plate unless anyone tells me it will damage something (just till it gets here). I also have a question about the catlitac converter. Has any one removed it completely without problems? Dont think mine is stopped but trying to prevent future problem. I have a fab shop with the tools to do it. Thanks to everyone for being so helpful and i will let you know the results after installing the parts. I could also use a diagram of the vac lines on the throttle body just to be sure P.O. didn't mess them up. They just look tampered with.
Put the EGR on, the computer expects it to be there, and working. Leave the cat. converter on. The exhaust will be loud without it and I am speaking from experience. You will gain nothing in removing it. Will it harm the engine if you remove it? No.
So, how does it run now?
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Originally posted by Chris38:
Got the coils and pim off. Pim tested bad at oreilly auto. New pim New coils just to be safe And new crank sensor will be installed tommorw. Also the egr valve was bad. This part was special order so i am going to use a block off plate unless anyone tells me it will damage something (just till it gets here). I also have a question about the catlitac converter. Has any one removed it completely without problems? Dont think mine is stopped but trying to prevent future problem. I have a fab shop with the tools to do it. Thanks to everyone for being so helpful and i will let you know the results after installing the parts. I could also use a diagram of the vac lines on the throttle body just to be sure P.O. didn't mess them up. They just look tampered with.
UPDATE Thanks to all the input the duke is back running. Basically all of you were correct. It had many problems Pim was bad Coils had a small crack Egr was completely shot Map sensor was out Even exhaust had a crack but i welded it up. I dont even know how it was running at all. It runs very good more power than ever. Although i had to install a egr delete plate because parts store ordered wrong part. Now i have to re order it (they claim they can not get it). Drove it 20 miles service light came on once then went out. Probably due to egr gone? But it ran amazing. For now lol I can't say enough thanks for all your help on a system i have never worked on. A big THANK YOU to everyone. Now if i can just find a vacum diagram for the TB. P.O. has the map hooked to the intake and one hose(largest one off TB is just plugged. Even though it is running great something looks tampered with by P.O. my cheap manual doesnt seem to have a routing. Will check code tommorw just to see what code it shows. Meantme gonna try to find a tbi vac line diaphragm.
