Hi TGO friends,

I have a 1990 Pontiac Firebird Formula with the 305 engine, TPI, and I recently had new head gaskets installed, installed new pushrods, rockers, all intake gaskets, cleaned all carbon from intake, pretty much replaced all worn parts, etc. all installed according to service manual, followed all the torque specs, etc.

Also have new exhaust and cat. converters.

The passenger side exhaust is running "cold", around 200F, while the drivers side exhaust is around 500-650F, so there is a difference of 400F degrees between exhaust manifolds measured with an infrared thermometer

I understand the 500-650F temp is normal, while the 200F does not seem normal to me

- Timing was set to 6 BTC
- Can't hear any misfire
- Knock count stays at 0
- No error codes
- Tested resistance of injectors, all have similar resistance, 14.8 ohms
- Cat. converters also differ in around 100F from each other

I ran out of ideas.

Any help will be appreciated

 

Does the engine run smooth?

 

Yes, it looks smooth to me and several people that have looked at it.

I did a compression test BEFORE taking the heads out and all the cylinders had around 165-170 psi.

Thanks

 

I have recorded a video to show this problem

 

Your bank 2 injectors aren't firing. Check 12v power supply to bank 2 and ECM ground pulse to bank 2.

 

Wouldn't that make the engine run lean and be noticeable in quite a few ways?

 

No way. Nothing with half the cylinders not firing runs that smooth. Get a spray bottle and shoot a little water on it. It should sizzle off almost immediately. If it just sits there and slowly boils away, yeah, it's definitely cold.

Agreed with others, one bank of injectors not firing would be the only thing I could think of that could cause a whole bank not to be firing. I mean unless you got all 4 plug wires on the wrong plugs on that side. Still, it would be barely running if either was the case.

 

Maybe the air injection is only working on one side.

 

Only one O2 sensor, and it's in bank 1.

 

Thanks everyone for your comments.

I just did the "screwdriver" test, but instead I used a stethoscope and in fact, none of the injectors of bank 2 are clicking.

Oh crap, and I drove like this for 5 miles this weekend.

I checked the fuses for INJ #1 and INJ #2 and both are good, and both show 12V passing through.

Will need to continue troubleshooting, if anybody has an idea, it will be greatly appreciated as always. Good thing is I have the service manual

 

If both fuses are good, check for 12V right at the injector connector. If yes, then either the trigger wire from the ECM is open, or the driver in the ECM is shot.

 

Hi and thanks for your help

Both wires in the injector connector are at 12V, so it seems to be a problem with the ground pulse from the ECM, from what you are saying? Either the wire or the ECM itself? Thanks

 

On injector connector, pink/black wire should have 12v whenever the key in on. The green wire should have nothing with key on/engine off, but ECM will pulse ground here with engine running to fire injector.

 

Thank you, I followed the diagnostics in the service manual and it seems circuit 468 (Dark Green cable) is open.

Will keep you guys posted

 

This has been fixed. Thanks everyone for your guidance and help!

The injectors of the passenger side are firing for the first time after this big repair

 

Don't be so sure about that.....I accidentally ran my Express van on 4 cylinders one day after messing with a valve cover I never put the plug wires back on the distributor. Took me some time to figure out why it idled/ran smoothly but fell on its face under load. It was still dead smooth under load, just no power.

 

I am with Damon, and that is what confused me, because I never thought an engine working with half the cylinders could run so smooth, so I never even considered that option. I thought the same, there is no way this engine is running on 4 cylinders only.

However, after eseibel67 brought it up, I gave it a try and he was absolutely correct.

I think this is a lesson learned that we need to have an open mind when troubleshooting engine issues

 

Thanks. I appreciate you sticking up for me even though I was dead wrong.