Irratic idle. Is it injectors?

[Rowdy45466]

Hey all, my 87 has an irratic idle. TPS is ok, new O2 sensor. It has a chip for 42lb injectors and that looks like what it has. It is making the car run lean then the computer dumps more fuel in and may be causing fuel wash to happen.

I would like to know if it is the injectors. I have put very few miles on the car since I got it. The injectors show electrically they are in line. It barely would start here in IL when the temp dropped to 40 degrees. I guess if you hold the brake and rev it a bit and build boost it runs well.

It has a new fuel pump as well with the hot wire kit.

Motor looks to have been rebuilt and the car has alot of upgrades including Hooker Super Comp headers,high flow crossover, a 3" downpipe,test pipe w/dump,3" dual muffler exhaust,adjustable waste gate rod,ESP front mount intercooler torque strap,B&M linelock,2004R w/Trans Go shift kit and billet servo (shifts very well) 9.5" 3500 stall,SFI flexplate

Also what should a compression test show for the cylinder pressure. THis is all with in a few % of each other around 130psi.

Normal?

What about hot idle oil pressure?

I'd like to maybe upgrade the chip, injectors, and throttle body.

What size would you go with to have a low 12 high 11 second car and would it still be driveable. Idle ok ect.

Thanks,
Rob

 

[QUIP'6']

42 pounders are very tricky to get to idle smooth eric marshall may help if not go with 60 pounders

 

[Lee_Burough]

Rob...

An erratic idle is most likely to be a vacuum leak. I'd spend some time eliminating that possibility first. Then, a modern chip.

You are all over the place about the gaps in your education. Poke around at Steve Woods site and GNTTYPE.org and get up to speed on the basic things.

Do a Spring cleaning too.
You will find a Quick Reference for normal operating parameters there.

135 PSI is on the low side of normal, as long as the cylinders are pretty consistant, its OK.

Clean your injectors with zylene, K-44 or Chevron Techron Fuel system cleaner, (look here for a do-it-yourself injector cleaning via the rail.)

 

[87NAT]

Change your fuel filter, clean your IAC.

 

[jretrodude]

Make sure your computer isn't on it's way out?

I had the same issues as you and I think it was my computer because it went out when I was troubleshooting the idle and dying problem. I put new injectors in mine and new fuel pump. So???

 

[PowerKraus]

You have received some good advice. IF none of these suggestions remedies the situation, double check your spark plug gaps.

I know I run a tighter gap than stock and it does cause an irradic idle.

 

[its turbo time]

I had the same issues as you and I think it was my computer because it went out when I was troubleshooting the idle and dying problem. I put new injectors in mine and new fuel pump. So???

damn im having the same problem with the idle and dying hopefully its not my computer!

 

[Rowdy45466]

How do you diagnose the ECM computer?

 

[Rowdy45466]

We have talked with the shop that is doing some of my work about the injector cleaning. They have equiptment that hoos up to you fuel system and runs it on their solvent for a while.

They get about 100-120$$$ to do this with the cost of the cleaner.

I could be putting that into new injectors.

Has a new gas tank, rubber hoses, and fuel filter.

New plugs,

New coil pacs and wire,

New airfilter.

 

[Lee_Burough]

Change your fuel filter, clean your IAC.

Then, check for vacuum leaks....You can clean your injectors pretty well by using the link I gave you above.

You need a spare ECM anyway, get one from Red Regal T and swap it out if you must....But, it probably won't be the ECM...Its more likely to be a bad ground than an ECM.

What are your BLM's at idle? I don't know what focused your attention on your injectors, but you seem real distracted by that possibility....Check and recheck the easy stuff before you spend money on a big item like injectors.

Post your idle values from a scan tool, and it should help the keyboard diagnosis a lot.

 

[Dreamcar86]

I agree with Lee on this one. Start with the basics and keep it simple in the beginning and less expensive. Trust me there will be other things you can spend money on. Have you gone to gnttype.org yet? Do you have a scantool? You cannot own one of these cars without one. That would be a great place to start spending the money. I would go through the scantool and pull all the readings and see if they are in check. If not, that is where you start.

Hope this will help and like Razor always says "Keep it Simple". Do not over think it.

 

[Rowdy45466]

The ECM looks to be fine.

The shop working on it for now is asking me this or that that I don't know so thats why I may sound funny or have gaps in my story.

We found two numbers on the injectors. Also yes it was running rich and the computer was not able to lean it out.

The injectors were my friend and mechanics direction with the car. one said 621030 with a blue band at the top of a few of them. Another read D1163AA. I called a few places and finally I called Poston and the guy was nice enough to look them up for me even though it took 5 or more minutes and he had to leave the phone and go into the shop or? to find what they are. Finally he came up with 40lbs which is what the chip was suppossed to be for. He said the injectors were an older pintle type and they were never very accurate and even after rebuilding them the flow a wide range 38-42 all around. He said they were not really worth replacing.

A few weeks ago I saw a Hypertech chip for my car used with very little info and I gave 15 for it shipped. So the local guys at the shop asked me to drop it off yeserday. I did and a couple hours later I get a call and it is him saying the car is no longer surging and dying. In fact the computer is doing everthing normal and the read outs were right on, He also used some very blankety blank word to say is was seriously hauling the mail.

So do I leave that chip in, or order a new one?

 

[Lee_Burough]

That was a stroke of good luck!

I'd recommend you get everything running normally before you change anything. After you have a good baseline on everything, you can change one thing at a time until you work toward the place you want to be, performance wise.

I'd expect a lot of timing in that chip, use good fuel when you go WOT. If you decide to keep those injectors, get a modern chip.

After a fuel pump, the first modification I'd make is an Alchy kit (burn the new chip for Alchy too), assuming you don't have any overheating issues and your radiator is working well.

With the modifications you have, you're almost there where you said you wanted to be in your first post, performance potential wise. You are going to need some fancy tires to hold what you have now :biggrin:

Keep exploring the site links I gave you inmy first post....

 

[Rowdy45466]

Thanks Lee, and everyone else. I'm hoping for some drive time this weekend. I still may have a larger issue of the oil being burnt. Not as much now but still some.

A few have said my compression may be on the low side.

But I do plan on alcohol and more boost and bigger injectors as long as it is streetable.

I'll be posting my impressions after I get some drive time and generate some tire smoke.

Rob