The basic story is I've got this 87 Iroc with 58,000 miles. It sits pretty much 360 days a year, the other 5 days it spends on meandering country drives. Its all stock, except for K&N's, and an Edelbrock catback. Anyway here's the issue.
Whenever we start it after its been sitting a while, it fires right away and tries to run, then it dies after a second or two. It does the same thing about 3 times, then it'll start and run at idle... but its a rough idle. If you try to give it any gas at all it'll stumble and die. Once its run for 5 minutes or so its fine.

Yesterday I went thru and put in a set of Bosch Platinum plugs and an Accel cap and rotor. I haven't done much with this car cause it hasn't really been a priority. Since we only drive it once in a blue moon, waiting 5 minutes isn't a problem. But its getting on my nerves. There are no codes, the plugs that came out were all clean and evenly matched, so its not rich/lean, it doesn't smoke. It has a lot of minor leaks, probably due to age.

So has anyone had a problem like this? Any ideas? I don't have a shop manual for 87 so I'm not exactly sure where to start. I suppose I'll set the minimum air and TPS today and see if that helps. I also need to change the O2 but I'm not sure if that would cause this or not. The fuel filter has been changed a while back, less than 5000 miles ago. So I'm open to suggestion.

 

you might try changing the fuel filter sitting that long their might be sediment building up in it.

 

sorry i am an idiot didnt see the part about already changing the fuel filter

 

I had something like that, it was a vacuum leak. Have u driven it on the streets and seen how it runs and acts at stoplights??

 

It runs flawlessly once it warms up, except that its a little slow to throttle response... it idles at 600rpm, right on the dot, runs a little rough, but its not missing.

 

my corvette kinda did what your saying, the fuel pump motor was breaking down, replaced it and all is well.

 

That's a possibility but it doesn't explain why it runs perfect once it warms up...

Any thoughts on whether the cold start injector could be related to this?

 

i dont really think it would be the cold start, but on the fuel pump, the only way i could really explain it is once it catches its "groove" it will keep running, then sometimes the motor shorts out and starts to work in pulses and eventually shuts off until the 12V is shut off and reapplied. id definately stick a fuel pressure gauge on the fuel rail while the symptoms are occuring before i changed the fuel pump on a 'roc. changing the fuel pump on a tpi vette is childsplay compared to the tpi camaro.

my reason behind the cold start is that usually when those things go bad, it just causes it to run rich and blow smoke, i dont think ive ever seen one cause an engine to just die.

 

hmm... the symptoms are pretty similar to the problems I had in my S10 when the fuel pump died... that might be it... if I feather the gas it'll rev up a little, but if I push it any farther than the minimum it'll die.

 

definately sounds like a fuel delivery problem to me. theres no hard starts associated with this at all? if not that rules out injectors.

 

Drew,

This sounds SO familiar. I had the same thing on my '86 when it had only 22,000 miles after eight years (1995). It sits almost all the time.

I chased around the problem off and on for a couple of years. New ignition parts, plug wires, compression tests, valve spring inspections, cam lobe check with dial indicator for worn lobes, fuel pressure, fuel filter, countless TPS adjustments to slightly different settings, new O² sensor, new vacuum lines everywhere, new coil, new pickup, removed/cleaned EGR valve, tested MAF, new PROM, wiring inspected, more new ignition parts - the list goes on and on.

The idle only had an occasional "miss" and there was an unwelcome hesitation from a stop. I finally did a power balance test to identify the weak clyinders. I identified two cylinders that had a slightly different RPM drop when disabled. I closely inspected all the ignition components on these cylinders, replacing even more "suspect" parts.

I finally performed the power balance test on the injectors, and discovered my problem. One of them was making a definite no-change in the idle when it was unplugged, and one made very little change. I rigged a solenoid tester/actuator and manually fired the suspect injectors with very long pulses, and surely enough, the idle was more affected. The car always ran well once it was off idle, probably due to the longer injector pulses and eventual flow through the suspect injectors.

What had taken me so long to determine this was that the injectors were supposedly "cleaned" at the dealership with one of the flow-through injector cleaning systems at 18,000 miles, so I never suspected a problem there - DUH!

I removed the injectors and sent them to Rich at Cruzin' Performance and within two days I got an email back saying that one injector was flowing 38% off spec, one was off 16%, and another was off only 8%. The rest were within 3-4%, wich the factory considers "balanced". I got all mine back after they were adjusted to 1-2%.

The car never acted that way before - it was like a new engine. No hesitation, more tire-smoking torque from a dead stop, smoother idle and cruise, better accelleration, and even less audible detonation when accellerating (probably since some cylinders were no longer lean).

I'm not saying that your problem is injectors, but if you exhaust all other possibilities, it could be a problem. A fuel pressure gauge and 'noid tester are good diagnostic tools in finding a poor flowing injector, but they have to be pretty bad to find them even that way.

I spent less for the premium service from Rich than I did at the dealership for inferior work, and got ten times the benefit. This was all at 22,000 miles. Discussion with Rich led me to believe that all the sitting in the garage under the cover really wasn't doing it any good, and may have contributed to depostit formation. That's another reason I try to start the engines on all my stored cars at least once a month while in storage.

At least it's a possibility.

 

hmm... I got used to injector problems with my V6 bird, and none of the symptoms seem to match... all the plugs are perfectly matched, so I would believe all cylinders are burning evenly. I'll check the fuel pressure and do some more tuning today and see if that helps at all... I might just need to take it out and flog on it a bit and see if it gets any better...

It disturbs me that its a fairly obvious problem, but the ECM isn't catching it and there's no obvious culprit.

 

HEY! I just noticed you are in Sioux Falls. I made the trip there once with this same car (after the injector cleaning). It's 540 miles from the Illinois/Wisconsin border. I made it in 6 hours, 35 minutes to a softball tourney - you figure out the average speed. All I can say is that anything over 90 MPH in an 'F' car almost requires that you have the 'T' tops installed or the rear end gets really loose and squirrely. Driving across Minnesota on 90 I was passed by an old lady in a Cavalier, and I was already doing about 80. I figured it was time to make up some ground, and you can see ten miles ahead in some of the really flat areas there. Needless to say, I made up some time.

 

Drew,

My ECM didn't catch anything either. Since the injectors are batch fired and the ECM only gets one averaged O² input, it will adjust the other injectors just a little "fatter" until it is satisfied.

If you had an OBD-II system it would catch the misfires on an individual cylinder and make the diagnosis just a little easier, but our older systems just don't have that much sophisitication.

Maybe if you made the same run I did in reverse, it would clean things up a bit. Have you tried ethanol-blended fuel? I think that has helped me keep cleaner injectors for the past seven years - that and the little bit of two-stroke oil I add to the last tank of fuel before storage along with the Sta-Bil. I'm thinking the oil coating on the injectors may be helping to prevent or at least retard deposit formation. I've been doing this for the last two seasons as an experiment. I've consulted Rich who advised me that it wouldn't hurt the injectors at all. Neither of us knows if it will work, but I'm the guinea pig. So far it hasn't caused any problems and I may find out in the next few days if the car still runs the same - time to take the insurance off suspension and go back to full-coverage so I can play.

 

hehehe yeah I90 across Minnesota is 70mph, and I90 and I29 here in SD are 75mph. Triple digits aren't too difficult to get away with, especially early morning or late at night. At night you have to watch out for deer and the HWY patrol.

I'm thinking it might be a fuel delivery problem and might be from sitting too long... I use Stabil in all my cars since they all seem to sit indefinitely from time to time. If you think of anything else let me know... I'm off to bum tools...

 

I use Sta-bil in the gas if it is going to sit for few months. Also if
the battery goes down below 10 volts while the car is sitting in
storage, the computer memory may loose it's fuel trims that it has
stored. After the car runs for a while the computer relearns what
to do and everything is fine again. And no, while 9 volts like used
with a "memory keeper" device used for changing batteries is
enough current for short periods, it is not enough to combat
long term memory degradation. If a battery drops below 10 volts
for more than a couple of months you stand a risk of loosing
stored memory. Try using a battery maintainer that puts out like
1 amp on the car while it is in storage, just to keep the battery
fresh.

 

Does it act up whenever it's started or just over a period of storage. Get it out on the road--putting some miles on it may be all it needs! There's only 3 IROCS left in Watertown that I know of...#4 just took out a light pole, mailbox, and a fire hydrant last weekend...Drunk driver doing 50+ down a side street on ice...

 

To be honest I couldn't tell ya since I really haven't driven the car in about 2 years. We usually pull it out, change the oil, wash it, and drive it 30 miles, then park it in the garage where it sits for another several months and then the same thing repeats. Back when I used to drive it, the car ran good but had charging problems. An alternator and battery solved that problem, but since then I've had my formula, my convertible, and my V6 to mess with. The Iroc didn't enter my mind again till I moved home when my marraige went to ****. Now that I see it everyday its hard not to work on it since I know its a fairly unusual car and it deserves to at least be in tip top tune.

Somewhere in SD there's a really sharp 87 Iroc. It was at a carshow in Madison a couple years back. It had about 20,000 miles, all original, L98, ttops, etc. It was red with gray interior. I havent seen the car since.

 

"Somewhere in SD there's a really sharp 87 Iroc. It was at a carshow in Madison a couple years back. It had about 20,000 miles, all original, L98, ttops, etc. It was red with gray interior. I havent seen the car since."

That would be the car I have been looking for. I can imagine what some1 with a 20,000 mile IROC-Z would ask for it though.

 

Get this though, the kid that owns it can't be more than about 17, 18... Considering what it costs to insure an Iroc, I can't imagine he paid anywhere near what its worth.

 

Wow.

Yeah, he had to pay alot, even more if he wasn't familiar with what they are worth.

 

Well? Any progress? Just askin'...

 

Not especially... it sounds like a fuel delivery problem, and since the car isn't insured and it keeps snowing, we can't really drive it... and I haven't been able to bum a fuel pressure guage, so Im kinda stalled.

Right now I'm cleaning up the engine bay and trying to get everything routed correctly so at least it looks right...