Hi guys, I just bought a new 1989 IROC and I'm starting the trouble shooting process. It is having a bit of a strange issue. It is behaving like an absolute dog. It idles ok, however it seems not to hit right through the rpm range. Also after driving for about 15 min, it continues to run rougher until stalling out on deceleration or while at full lock. The steering is also fairly heavy. It has a new L98 crate motor and new injectors.

here is my Plan
1) replace spark system (off old motor with 225k)
2) check spark plug gap
3) adjust timing
3.5) check power steering fluid
4) check fuel pressure
5) ensure that injectors are not miss wired.
6) replace EGR

beyond that do you guys have any suggestions? I know the Smog diagrams for this car like the back of my hand, and everything seemed perfect. I also sprayed starter fluid around the intake, RPMs stayed steady which makes me think the intake manifold is mated to the block correctly. I also listened with a tube for vacuum leaks and heard nothing.

Suggestions?

Edit: I did have a manual before TPI 305, So I have never worked on an automatic. If there is anything I should know, assume I'm ignorant. I heard it may also be the torque converter or the auto's vacuum line.

Pics for those interested:

Great looking car!

Your list looks good to me, I would go ahead and give it a full tune up with new fuel filter and air filter, and it's never a bad idea to change all fluids on a newly purchased vehicle.

When it stalls out will it start right up again?

Your missing one of the most important pieces on the front end.

^^It has the air dam underneath if that's what you mean.

I think he was talking about the chevy nose badge?

Thanks! It was a really great find. I only paid $2800! xD

I'll do that. May be a fuel filter now that I think on it.

After it stalls out, it will start, but the RPMs drop until it dies. You can keep it running by giving it gass (which seems like a lack of spark or fuel to me).

Haha yeah, where can I get a nice one?

Edit: it's an '89

Could be a low fuel pressure problem? Maybe once the pump gets hot it slows down. Or it could be spark related also...

I would do the tune up with the things on your list and check fuel pressure when the sympto s start.

+1

Update:
Just changed out the entire spark system, still running rough and having no power under load. Will check fuel filter then fuel pressure and report back.

Thanks for the input.

Could be bad or dirty injectors.

What all did you replace, and did you adjust timing?

I had a tbi car a few years ago that the previous owner had done the timing, but with the EST wire still connected so it ran like garbage.

Coil, wires, rotor, cap and re - gaped plugs to .35, also timed it to about 15 degrees advanced, where my last camaro ran best.

It has brand new O'Reillys replacement injectors. So I doubt it. It's more likely he cross wired an injector. How would I find out if he did?

The injector wiring is in order to how the injectors sit

Make sure the egr valve isn't open at low engine speed, this will cause it to stall/run rough. It could be the egr control solenoid is allowing vacuum through.
Make sure the timing advances when you rev it.
Check the ecm grounds, these are at the back of the engine.

Update:

OK so I just changed the fuel filter (which he had in backwards), and checked the fuel pressure. The fuel pressure seemed fine. 42 ish while idling and 36 ish when revved. Stayed at 46 with the regulator disconnected. Seems congruent with what I have seen on previous threads. Checked the injectors, none are sticking. Now I'm letting it idle with a tone of injector cleaner in to see if that helps.

With the way the wiring harness is designed, the injectors leads for any two adjacent cylinders leave the harness at the same point, making it difficult to tell. When I swapped the injectors on my last iroc, I took a sharpie and wrote the cylinder number on the lead.

"Now I'm letting it idle with a tone of injector cleaner in to see if that helps."

You said earlier you had "brand new" injectors from O' Riellys ??????

The injectors are batch fired; all four injectors per bank fire at the same time.

Mixed up connectors shouldn't be an issue. Unless they somehow got swapped over to the opposite side of the engine, which is unlikely.

The fuel filter was in backwards, idk if it even works backwards. And he was trying to run it on 3 year old gas. God knows what might have gotten into them. Just trying to eliminate all possible factors.

Then they're obviously fine. I was only concerned that adjacent injectors were miswired since I thought it was a sequential injection system.

I just read this in the injector swap article, can someone post a tech article on how this works? How can all injectors on one bank be fired simultaneously if not all the pistons are at bdc for their intake stroke. Doesn't that cause bogging the same way improperly timed spark would?

Update:

With the EGR plugged off. It runs, but just barely. It still had no power and has trouble off launch.

To date I have:
1) replaced the entire spark system
2) timed it (roughly, about 10 degrees advanced)
3) changed the fuel filter and ran injector cleaner through it
4) I checked the pcv valve, it's fine (not relevant to the lack of power)


I have ordered new K&N air filters, will install them tomorrow and check the exhaust pressure before the cats to make sure their not clogged.

Other than that I will have to check the TCS (revving with a timing light, making sure it advances), do a tap test on the ecm and check it's ground. And change the EGR, if that doesn't solve it. Other than that, I'm out of ideas. Suggestions?