MikeM2

Got the 89 Formula 350 home and now starting to tackle a couple issues. First is a bad miss I need to get taken care of. Car starts up ok, but it won't idle when cold and has a bad misfire and pops through the exhaust at low rpm. Give it gas and it smooths out fine. After the car warms up, it runs much better.

previous owner installed new Magnaflow exhaust with no cats. Stock manifolds. Also has a cold air intake. Did not do anything as far as a chip.

Car are smells like it's running rich.

Any thoughts as to where to start?

its a 5.7 TPI car.

Thanks.

red rock

iTrader: (2)

First, start with the basics. Plugs, wires, distributor cap and rotor, coil. If you haven't done so already.

MikeM2

Plugs, wires, cap are all good. Even after it warms up, it still has a little hesitation and will backfire when you hit the gas from low idle. Shoul he have changed the chip with the exhaust and cold air intake?

Or maybe a sensor or ??

red rock

iTrader: (2)

No chip tuning needed. You are basically stock. Check the header above in the "how to's" section to learn how to set the IAC and TPS. Vacuum leaks are a big problem with the TPI intake. With the car idling, spray carb cleaner around all gasket areas on the plenum, intake manifold, TB and runners. If you notice a change in idle, that's a vacuum leak. Check all vacuum lines for cracks. Are you setting any codes? Check engine light on?

MikeM2

OK - thanks. I'll start chasing vacuum leaks and see what happens.


Going to take advantage of these rare nice days in Wisconsin in February!

Tuned Performance

iTrader: (92)

The backfire could also be from leaking injectors, if it's only cold it could be the ninth injector. But it sounds like you may have a few injectors that are bad.
Ohming the injectors warm maybe a way to tell if the coils have broken down.
15-16 ohm is where they should read.

red rock

iTrader: (2)

Where in Sconnie are you? If you are close enough, I could help you.

MikeM2

I'm near Lake Mills - East of Madison


Probably going to replace the original injectors anyway so any recommendations as to which ones to use? I hear over and over that the stock injectors are not the best.


Thanks.

MikeM2

Oh - and no SES light on. Don't have a code reader yet but the car sat all winter with the negative cable disconnected. The light hasn't come on in the couple days I've owned it.

Tuned Performance

iTrader: (92)

Got a paper clip ?

Tuned Performance

iTrader: (92)

http://www.obd-codes.com/faq/read-gm...codes-free.php

MikeM2

Thanks for the tip! I'll give it a try.

red rock

iTrader: (2)

There are many injector vendors all over the map. Here is a TGO vendor that is good. https://www.thirdgen.org/forums/afte...ors-cyber.html And I'm way up north, so to far to lend a hand.

TylerSteez

iTrader: (3)

I also recommend southbay injectors. I'm currently putting them in my car. great company ran by very good people.

southbay08

Thanks for the thumbs up guys... Of we can help in any way please contact us

MikeM2

Ok, well I set the IAC and the TPS as described. No change. Sprayed carb cleaner all around the intake when running, no change in RPM or noticeable difference. Even when its warmed up, the idle is erratic. Up and down all the time. Above 2000 rpm everything is fine (when its warm - cold is a problem regardless of rpm). I did hear an odd rattley gurgle sound when its running. No laughing, that's the best I can describe it! Sounds like it may be coming from inside or directly under the upper part of the TPI.

Never had one of these apart but looks like I'm going to learn. We'll see if that's anything to be concerned with. Looks next step is injectors. What pound injectors should I be looking at? Thinking 24 lb?

Thanks again!

red rock

iTrader: (2)

There is a vacuum line that runs and connects from under the throttle body and goes under the plenum to the EGR solenoid. Stay with the stock size injectors if you plan on staying with a stock type engine. Should be 22 lb. Here is a diagram. http://www.chevythunder.com/fuel%20i...um%20lines.htm

MikeM2

Couldn't see any obvious vacuum leaks under the plenum and it appears everything is connected. Put a fuel pressure gauge on the rail tonight. Turned the key on without starting the car and had 40psi. Started the car and pressure remained at 40psi at low rpm but dropped to 37 with throttle open. (Have to play with the throttle to keep it running when cold still). Shut the car off and it held at 40 psi right away but then krept up to 43 psi. Is this normal? Held there for 10 minutes until I pulled the gauge off.

Thinking the fuel pump and lines are good based on this. So IAC, TPS, and fuel pump are good. Assuming fuel pressure regulator is good as well.

That said, I'm thinking injectors are next as soon as I get the cash.

How do I test the MAF sensor? I cleaned it but wondering if there's a way to test it?

Also wondering about the coolant temp sensor?

Thanks.

red rock

iTrader: (2)

Did you ohm out the injectors as was stated earlier? There isn't any good test that i know of for the MAF other than the two relays behind the brake booster

MikeM2

Did not ohm out the injectors. Haven't figured out how to do that with my meter yet. I may be leaning toward replacing the MAF. Its the original and I can see dark spots on the hot wire. Talked to the guy I bought the car from. He said it started acting up as soon as he put the cold air intake on. It has a K&N filter on it. He said that he oiled the filter with the K&N recharge kit right after he put it on. Thinking he put too much oil on and it sucked it through the MAF. I cleaned it but maybe its already junk.

red rock

iTrader: (2)

Have you checked for codes stored in the ecm? The burn off relay burns off impurities in the MAF when working properly. I wouldn't just throw money and parts at it unless you know what to replace. A cheap MAF is anywhere from $150-$200. A reman is junk. You unplug the injector and ohm across the 2 pins. Use MAF sensor spray for the MAF. Clean the K&N and don't oil it too much. I have used K&N type filters for years and never had a problem. If your fuel pressure held for any length of time, your injectors shouldn't be leaking. In my experience with people, if the previous owner thinks he has the answer, then he could have fixed it himself. It's yours now and you have to do a lot of testing and diagnosing to figure things out. A good factory repair manual is a godsend, and then a chiltons or haynes are the next option. There is also a ton of info on this site. The ECM codes are a good start but if no codes are thrown, then it's basic non ECM issues like spark, fuel. One way to check for spark jump, is to run the engine in pitch dark and look for a spark to ground. Or check all your plugs to make sure they are all burning the same color. Anyway, we'll keep helping as much as we can. Good luck.

Springster

+1 for dirty injector(s). The spray pattern is not atomized enough to burn. When cold, causes no or rough running. When the engine heats up the fuel will burn but can cause back firing. Check plugs for carbon fouling and check exhaust manifold for fuel stains where it connects to the head. +1 for Southbay. I'm running the Ford injectors in my V6. A sin but it works great.

MikeM2

Went out to the garage and took a couple more swings at it. Didn't test the injectors yet but I fired it up again and warmed it up to get ready to test them when the SES light came on. First time its come on for me. Code 22 (TPS or low voltage) I did reset the TPS as outlined on this site and got the TPS set right. Can it test out at the proper voltage and still be bad?

Thanks.

Tuned Performance

iTrader: (92)

The grey wire is the ecm 5v reference. The feedback is the blue wire .54v at idle.
http://chevythunder.com/tps_code_22.htm

MikeM2

Ok so finally getting back to the car. Checked voltage on the TPS and it all checked out fine but still getting the same code. Went ahead and bought a new TPS from O'Reilly. Put it on but couldn't get the voltage to adjust below 1.2 no matter where I positioned it. Took it back to the store and they swapped it with another one, same thing. Can't get voltage below 1.2. Am I doing something wrong? Put the old one back on and it adjusts just fine to .55. Do I need to do something different when adding a new one?

MikeM2

Also - I just read in another post, that when I put a jumper between the A and B pins on the under dash connector, my electric fans should come on with the ignition on. Mine does not come on every time. Only every once in a while. Should the fan be on every time I jumper these and have the key on?

Thanks for your help on both of these questions!

Tuned Performance

iTrader: (92)

Unless your tps has a open in it I'd put it back on. The fans should always come on in diagnostic mode this could be a bad ecm.

MikeM2

OK so maybe I'm crazy. Now every time I put it in diagnostic mode, the fans are coming on. Who knows.


Found out that the O'Reilly's part number didn't match for that brand of TPS. Ordered a different brand and we'll see if that works. It was an error in their system. If that doesn't work, off comes the plenum and we'll take a good look for vacuum leaks.

MikeM2

OK so here's another question. Still tracking down the same problem. The guy put a set of aftermarket gauges (pillar gauges) from Summit on the car. Tracing wires, I find new wired attached to what I think is the temp sensor? There are two wires. One attaches to the drivers side, just below the exhaust manifold toward the front of the motor. The other wire connects to a factory wire that runs under the car. Both are routed up and over the motor to the passenger side, toward the rear of the motor and to some sort of switch or sensor on the block on the passenger side, below the exhaust manifold. Is there a temp sensor on both sides of the car?? I can't get my head in to position from above or below the car to see what the passenger side switch or sensor is. Sorry to be vague but I can't find what these two switches or sensors would be. No idea if it has anything to do with my problem but I'm tracing everything.