Ok, i need some serious advice here.

I am the unfortunate owner of a 1986 Chevrolet Celebrity with the 2.5 (iron duke/Tech4) engine. it is fuel injected (TBI), with an 3spd auto. I cant figure out why it wont start and when it does it runs like @!#$. the engine , when it does run, has a steady miss under light throttle at around 1800-1900 rpm, it will continue to miss until either -

a) floor it , which after it misses it sounds like all the cylinders are missing like a chugging.
b)let off the gas which then the RPMs will drop to the point of it dying,

but it starts right back up.

also it misses very bad when it is cold and as of right now in 10° weather it will not run at all. i paid a mechanic to fix it and he couldnt figure it out , all he did was change the MAP senseor and coolant sensor which seems to of made it worse . it is getting good fuel and spark also.

I have replaced the following-
-Distibutor and cap
-plugs, wires
-MAP sensor , coolant sensor , fuel filter, ECM

i know that the TPS sensor is good, the o2 sensor is working but is inaccurate , EGR is good also. but it should still start! the only thing i think might be causing it is something that controls the air/fuel/timing

sorry for length of post! i appreciate any and all feedback/ideas
Hell maybe i should just scrap this POS but i need a winter beater fast!!!! im getting soo frustrated with this abomination!!!!

maybe a clogged injector?

The Iron Duke is the god of all engines, while I had one on my old S-10 and had replaced everything on it....I cannot recall back far enough to help you.

Definately not the EGR, I had mine blocked off and it ran fine.

yeah im really clueless right now. i looked at the injector and it is squirting plently of gas down the TB ....any other ideas.

Sounds like the distributor module is going bad. When it is going bad it does exactly what you are describing. I have been saddled with 6 iron dukes over the years, so I've been able
to go through this before.

I used to own a 1982 Buick Skylark with the 2.5L TBI Iron Duke engine. Sounds like a vacuum leak. The throttle body mounting plate gasket maybe gone, or the aluminum throttle body has warped and created an airgap. I used a can of carb cleaner and carefully sprayed around the base of the throttle body to see if I could find the leak. The vacuum leak on mine turned out to be the mounting gasket for the EGR valve and the EGR valve itself.

"...nevermind maneuvers lieutenant, just go straight at them!"
-Admiral Nelson at the Battle of Trafalgar

sounds like you've got the same problem my 2.5 has. unfortunetly, i think ours is a compression problem. it's a constant miss on cyl. 3. single injector, so if one's not firing, neither should the others, or they should be random. replaced plugs, wires, and coils. nothin. i have yet to pull the vavle cover off to check the valvetrain, or the head. vaccuum lines seemed fine, but i agree, check those. and when/if you find out what's wrong, post it! i wanna know.


Andy

it's not how fast you go, it's how you get there that counts.
ZZP XP cam, 1.6 rockers, 105# springs, speedbuilt FWI, 3.3" modular pulley, TOG headers,
3" exhaust, flomatched injectors
'97 GTP 14.06@100.6mph pre cam w/ 3.5" pulley, I/E

My Dad's LeSabre did something like this a while ago, the Crank Positioning Sensor was cut in half, and then the new one was the wrong one, so I'd check that out.

I still say ignition module, would be willing to bet money on it.

yeah Marked 8 the only thing with the ignition module is usually what happens is it will get hot and then shutoff and not restart until it is cooled down. it puzzles me becuase i had the ignition module go out on my 2.2 TBI cav and what happened was eventually it would not start at all either. but the distributor has been replaced recently by the previous owner. i assume that he would have replaced the ignition module at the same time considering they are attatched.

and thanks so much for all of your replies, ive gotten some new insight as to what the problem may be, im looking for someone who has had this problem before and has actually fixed it because even on the s-10 forums people with the duke are having the same issue.

What im wondering also is has anyone ever had an ignition module cause a car to miss and hesistate really bad?

here's the kicker with mine, it's an '86 century with the iron duke in it... and coil packs! the '86's had distributors, but mine's got a coil pack. is yours a random miss? or is it on one cylinder. i think my cars got a compression problem


Andy

it's not how fast you go, it's how you get there that counts.
ZZP XP cam, 1.6 rockers, 105# springs, speedbuilt FWI, 3.3" modular pulley, TOG headers,
3" exhaust, flomatched injectors
'97 GTP 14.06@100.6mph pre cam w/ 3.5" pulley, I/E

ha thats crazy to have coil packs on an old duke, maybe it is newer a -code iron duke swapped into an older car. When i first got the car it sounded like it just had a steady miss in one cylinder. i havent done a compression test tho because i dont have a gauge

any other ideas?

could be wrong order on plugs on dizzy. And they can also be 180 degrees off.


____________________
1991 Honda CRX si mini me swapped

my buddy jason has a cutlas calas... im suprised that thing still runs. serously. he drove it with the oil cap off

Hey J K (91_CRX) what do you mean when you say that the dist could be 180° off?

turn it around the timing is off if the distributor is 180 deg around. Try turning it 180 degrees and then try to start it. It will still turn if the timing is off but it wont fire. just a thought tho



Thanx Charles

this is gonna sound really crazy, but have you checked your valvetrain? maybe one of the rockers was backing out, causing the valve to not open at the right times, then eventually just either broke or came off. i know, it doesnt sound likely, but anything's possible.


Andy

it's not how fast you go, it's how you get there that counts.
ZZP XP cam, 1.6 rockers, 105# springs, speedbuilt FWI, 3.3" modular pulley, TOG headers,
3" exhaust, flomatched injectors
'97 GTP 14.06@100.6mph pre cam w/ 3.5" pulley, I/E

Check the compression. My old celebrity did the same thing and it was a bad valve.

Would it not run if it had a bad valve or would it just be one cylinder?

i had a 86 celeb with the 2.8v6. that car was indestructable.


good luck.

Anyone else have this happen to them and know how to fix it please!!!! or just keep the ideas coming thanks everyone so far!!!!

If I remember right it has timing gears instead of a chain, I wonder if you might have had a tooth break off? A great resource might be the grand am owners club forums, they have a section for the 2.5 engine. I found them useful with my old 90 Grand Am.