Have a bone stock Blue 1986 Iroc that is throwing Code 36.

Original Symtoms:
- The car doesn't idle correctly.
- When pushing down on the throttle it has no response and then takes off.
- Sitting at a red light the car shudders, the tach drops from 750 to ~575-525, and the volt meter drops with the tach.
- Ocasionally when I come to a stop the RPMs drop ~500 and jumps back up and a few times the engine has cut off.

Diagnosis:
According to my Haynes manual this has to do with the Mass Air Flow Burnoff relay. I have read on the forums that this relay is different from the Mass Air Flow relay. However, both relays have the OEM #14078907 in white. I check a different White 1986 Iroc and both the relays have the same number.

Action:
I know the relays in this one are OK so I take them out of the White Iroc and put them in the Blue Iroc. I go for a normal ride and there is a definite improvement.

Current Symptoms:
- When pushing down on the throttle it has a slight hesitation from stop but no where near what it was.
- Sitting at a red light the car shudders, the tach drops from 750 to ~650-600, and the volt meter drops with the tach.
- So far only once when I came to a stop the RPMs drop ~500 and the engine recovered.

I'm fairly sure the MAF sensor is good bc I took out the one from the White Iroc and put it in this Blue Iroc all before switching to relays. A friend suggested it may be the timing chain causing the rough idle at lights. The spark plugs, ignition wires, and distributor cap were replaced 6 months ago.

On a side note, working on this I noticed the fuel pump relay has been bypassed. A previous owner has run a wire from the positive terminal to the wiring for the fuel pump relay (between the MAF relay and MAF Burnoff relay). The wire is plugged in taped into the wiring plug that goes into the fuel pump relay but the fuel pump relay is not actually being used. I don't want to untape the connection because I have no idea why it is like that. I will be getting a new fuel pump relay but why would it be bypassed?

I'm not mechanically inclined so any suggestions/thoughts would be appreciated. Thanks!

 

I've also got an '86 Iroc and am troubleshooting the same issue(s). Same symptoms you are experiencing along with DTC 36 and a check engine light.

The fuel pump relay is there to prime the fuel pump when you turn the key on and keep the pump running while the engine cranks while the oil pressure switch is open. When you turn the key to "on" but don't start the car, the fuel pump should run for two seconds, and then shut off. It pressurizes the fuel system. You can hear it.

If you hear it, whatever is going on with the rigging at your FPR/fuel pump relay is working. It sounds like power is being stolen for another purpose; If you have time, I'd remove the jump. You can always put it back, but, something is up and that doesn't sound right.

If you don't hear the pump priming at key on, the relay could be toast. The car can still start, but may start harder than normal. This is because of a safety feature working in reverse; The oil pressure switch needs to sense enough oil pressure to complete the circuit for the fuel pump to run. The oil pressure builds up as the engine cranks, the switch closes, and power is supplied to the fuel pump. Otherwise, the oil pressure switch exists to cut fuel to the engine if the engine were to suddenly lose oil pressure, to minimize damage (and probably fire, too).

On to the MAF relays.

Code 36 is a failure of the MAF burn-off cycle to complete. When you shut the car off, the ECM cleans the MAF sensor by applying voltage to, and heating up the little sensor wire just like a little toaster element, red hot, and burns off any particulate junk that might have stuck to it while the engine was sucking air past it. The problem is probably the relay itself OR a connection related to the relay. If it was the MAF sensor, code 36 would probably be accompanied by a code 33 or 34 or MAF-sensor specific code. This is a summary of many nights of searching and seems to make sense with the results I've seen in my own vehicle...

My research suggests three things to remedy the issue;

1. The OE/factory relays suck, and at 30 years old, should probably just be replaced--all 3, maf power, maf burn-off, fuel pump relay . I'm weary of replacing original parts, but relays are under-hood electrical, and it comes down to being a safety/operational item. My old ones will get stored in a box somewhere.

2. If you notice the relay electrical connectors, they're not weather-proof like modern connectors. And, it's a known issue that the wire connections wiggle loose, break, and that the wire insulation begins to slide down. It's extremely possible you have an intermittent connection issue right there in one of the connectors. If you see or suspect any issues with the connectors, it's time to remedy that. TPIparts.net sells brand new connectors. At 59k original miles on my Iroc, the maf burn-off connector has a ground wire that's beginning to expose itself and several other wires just feel really loose in there.

3. Clean the **** out of all the MAF-related electrical connections. The MAF sensor itself has a connection right over the pulleys and next to the cooling fan; mine was pretty gross.

I don't recommend this, but on my car, I wasn't sure the connectors were plugged into the correct relays. In fact, switching the FPR connector with the maf power fixed my first issue of no fuel prime on key-on. The relays do indeed appear to be different, because the FP can't pull power off of one of the relays, but on the relay that apparently is designed for it, it can.

I switched the MAF power and maf-burnoff connectors for the reason of putting different stress on the connections. I shored everything up, smooshed a bunch of electric grease into everything and plugged it all back in. Went for a drive.

Holy smokes. Car never ran so good. I was planning on a short drive; went out and put like 70 miles on it. Stopped and shut it off a few times to see if I could get DTC 36 to re-appear. It idled smooth at stop lights, ran great at heavy throttle. It cold-started fine since then, too.

I hope that helps...I need to find a source for relays and stop by tpiparts.net, this will probably be ~$120 project in total. But if I don't have to have a stuttering car at idle, and if I can move on from "what the hell is wrong with TPI stuff today?" -projects, it will be well worth it.

 

Thank you for the reply.

When I turn the key to the on position without starting the engine, I do hear a noise for a second or two. I'm guessing that is the fuel pump pressurizing the system as you mentioned. It's not plugged into the FP relay but at least it is working. I have a new relay to install and will do that once I switch out the fuel sending unit (reads 3/4 tank when empty) and swap for a new fuel pump.

When it turns over it does puff out smoke from the exhaust system for a second but once it's running there is no smoke. I feel it is related to these issues but not sure how.

I have replaced the MAF relay and MAF burn off relay with new aftermarket ones. It has much improved the idling but the tach still drops, less frequently now, and I'm still getting Code 36. They are the same part number so switching them like in your case won't help my Iroc.

There is a decent chance the wire connections are loose. I know of at least one wire in the harness where the sheathing has pulled back a few millimeters from the connector exposing the metal wire. Would it be possible to reset the wires in the existing connectors or would I have to splice in an entirely new connector?

I will certainly be cleaning the connectors. Just last week the cooling fan ceased operating on the radiator. I'll be trouble shooting that system at the same time now. Fingers crossed this won't be a running issue for long.

 

On the smoke at startup issue, that's probably the valve seals beginning to wear out. Oil seeps past them into the combustion chamber, and then it all gets burned out when the engine fires, creating a puff of smoke. I've been told 305's are notorious for this, but your 350 might have another issue.

Are you clearing the Code 36 every time you try a fix?

I'm not familiar with OBD-I, if the code will persist for x number of start-up cycles even if the problem is resolved. I've cleared my code with each fix to make sure I'm getting a clean shot at testing everything I do to try to resolve it.

A loose connection will really bungle stuff up. Do what you can to tighten up those connections, I'm pretty sure that's my problem too. The MAF and related components are pretty simple, considering. Not rocket science...lol. But the electricity has to have a consistent path for it to all work

 

Here's a bit of a follow up. I had the Iroc with a mechanic a few months back and got a slew of new parts.
Fuel: Fuel tank, fuel pump, fuel filter, and fuel sending unit.
Exhaust: 2055 Hooker headers & wye pipe, 3" Magnaflow hi-flow Cat, 3" Magnaflow stainless Cat-back.
Other: Mini-starter, header plugs, retrofit R134a with new compressor, some I'm forgetting.

Asked him to test the harness wires for the Fuel Pump relay. According to him there was at least one wire that was no good, and I forgot to ask him to isolate which one it was. I'll have to do some testing later down the road when I find a proper wiring diagram and a multi-meter.

The computer is outputting Code 44 in addition to Code 36 now. Code 44 being lean exhaust which I have read on multiple threads will cause the motor to run hotter. I've reset the computer a couple times and they keep showing back up.

I've driven it around every other weekend for a couple months now, including 100 mile trips on the interstate at ~75mph avg. Around town she runs cool - normal temps even with A/C on. Cold starts aren't terrible, slight hesitation/delay throttle response from stop. On the interstate I'm between 2,700 and 3,000 rpm and temps between 220 and 260, having to shut the A/C off at the high end so it will cool back down. I attribute this to Code 44.

UPDATE: Found the reasons for both codes discussing my exhaust system. Check Post #20 to #25 on this thread for the solutions!
https://www.thirdgen.org/forums/exha...9-exhaust.html