So let me start by saying this is my first post. I have a 1986 coupe that was sitting for about 4 years since it was last on the road. You've probably heard this issue before, but that's besides the point...

I have done some tune-up work over the past few weekends to get her on the road. Everything is great until the engine warms up. After warming, it bogs out around 2200-2400rpms during acceleration. When it is in park/neutral or when it is cold (first 2-5 minutes) there are no issues. (not that I want to drive it before warming...)

I'll begin diagnostics with electronics. I retrieved a code (54) by jumping the ALDL port, and am wondering: Could it just be a bad relay? Or could it be that the Walbro pump I installed uses less voltage than OEM and can throw the code? That's probably a stupid question, but I'm just exploring every possibility before I turn a wrench.

Replacing the relay is really simple, so I'm going to try that in the morning. I'll update then.

On a side note, cranking takes a while when first starting. Also, when I installed the new pump, I meticulously cleaned the whole sending unit, and made sure all connections were secure when re-installing. I put a new AC Delco in-line fuel filter in as well.

 

I looked at the ECM firmware and it shows that you'll get a Code 54 if the fuel pump voltage is less than 2.0 volts, so something is obviously not right if you have that code. Try resetting the ECM to see if the code goes away (it might have been an intermittent problem). If the code doesn't go away, it's possible the wiring between the fuel pump circuit and the ECM is bad.

I HIGHLY recommend buying a fuel pressure gauge to see what's really happening.

 

I put a new relay in. It cleared the code and one problem is fixed.. No more long cranks to start it. Now that we're past Code 54, I'll be changing wires & distributor cap/rotor. (Needs it anyways, already gapped and installed the plugs.) But I'm leaning toward injectors as the culprit. Blah..

 

11 hour fix. That's a good start into the C4 word!

The injectors could definitely be a culprit. The old injectors were good for the day and age, but new types of fuel and sitting for 4 years had cause some havoc. General tune up and the injectors and she should be squared away.

Now... we need pictures.

 

You've got alot of other sensors and control devices to look at before pinning the inj as the cause of this perofrmance issue. Usually bad inj will cause poor running across the board...not just over a specific rpm. Thats more indicative of an air problem...too much.

1st... make sure fuel pressure and flow is around 40 psi key on...35+ eng running but never dropping below that. Steady needle on the gauge.

2nd...set TPS and test with a DVM for the range. It should not have any flat or dead spots in the travel.

3rd... ck temp sensor connectors, wiring. O2 sensor wire....EGR operation and vac line to the EGR solenoid and the valve itself.

1ST..(should have been) get a FSM. You are absolutely going nowhere fast if you are trying to diagnose a C4 without the FSM as a guide. You'll waste piles of money on "suspect" parts failures, trying to apply old school fixes to the computer generation and then still won;t find the problem. The FSM when followed takes you straight to whats wrong. NOT a Haynes (hyenas) manual, or a Chitlens manual....a real GM FSM available from a publisher with links here or on Flea-Bay.. Prices range $50 to $150 depending on CD or 2 book set.

here kitty kitty.....
anyone seen the cat?

 

I did a little research on the sensors wreaking havoc, I'll be going over those after I finish the wires/distributor to make sure the ECM isn't going into "closed-loop" fuel delivery. Eventually, everything under the hood will be serviced at one time or another, so dropping money on parts doesn't bother me too much.. Especially since it's going in the garage for the winter!

 

I wouldn't just start replacing parts. Chances are, there's not a lot wrong. In addition, I can change the injectors on my '86 in about 2 1/2 hours, start to finish, so if you never did it before, maybe 5 hours if you are handy.
Buy a O ring kit and fuel injector orings, and take the fuel rail apart a half bank at a time, and you will only have to pull one side of the runnners. Pick the right side.
Reassemble the rail in place, and it will save you about an hour.
Also, try to pick up a right hand 89 exhaust manifold. The EGR tube bolts on instead of that aggravating clamp that needs to be crimped back on.
Every time I do a valve adjustment, or play with the distributor, I am so thankful I did that a while back.