My car is a 1991 Z28, with a L98 in it. It is all stock except for Hedman longtubes and 2 1/2" true duals. I have been driving it for about a week now and am having some issues with it.

First off, it has an idle problem. The idle is a bit rough, but not terrible. However, when the car is under load and at operating temp, once it shifts into OD and the rpm falls around 1250 or lower, it acts like it's only running on 6 cylinders or something, really jerky. But once it gets up to about 1500rpm, it's smooth. I have ac plugs, accel wires, new cap and rotor, new O2 sensor, new IAC, and tps voltage around .53v. I changed from Bosch platinum plugs back to my AC's thinking this would fix it, but nothing.

Also, I have a terrible RAW fuel smell coming from the engine bay. I have yet to take the fuel pressure reading, as I do not own a guage at this point. My gas mileage seems to be poor, but I have not actually calculated it yet, doing that this week. However, the gas smell coming from the engine has me concerned. Leaking injectors? Bad egr valve? Bad FPR diaphram? Any suggestions?

Today while driving around, and sitting at idle in a drive through, the car threw me a Code 32, which is MAP voltage. I checked and I have no vaccum leaks of any sort, so I dunno what could cause this code. Could someone shed some light on this one? Bad MAP sensor? Thanks in advance for any info.

 

Get a new MAP sensor, they are cheap. As far as gas from your engine bay goes, of course that will hurt your economy, and you should search out the leak and fix it for safety reasons as well.

 

Excuse me for sounding so ignorant, but where exactly is the MAP sensor located? I have yet to change one yet, and I want to make sure I knwo what I am doing before I start tinkering with anything again.

 

Code 32 is the EGR code

Code 33 is the MAP code

 

From what I have read, it is actually both. It is the EGR code for EFI engines, but also says that it is the MAP sensor circuit open.

Code 33 says MAP sensor voltage low-pressure low, vaccum high. The shop I took it to last week said it was running on only 6 cylinders apparently. I'll have them take a look at it. Could the egr be the problem with the gas smell?

 

a bad MAP sensor won't cause a raw gas smell under the hood. that would more than likely be a fuel leak somewhere.
pull the dip stick & smell the oil, does it smell like there maybe gas in the oil? check your fuel pressure regulator by pulling the vacuum line off of it & pressure up the fuel system.
the FPR leaking some can cause what your describing.

 

What are you reading that states anything about the MAP Sensor Circuit for a code 32?

This is straight from the Haynes Manual:

Trouble Code: Code 32 (fuel injected models - except 3.1L V6)

Circuit or System: EGR System

Probable Cause: Restricted vacuum hose to EGR solenoid or valve; poor electrical connection, open or short in circuit; defective EGR solenoid; defective EGR valve; defective ECM

No where in there, does it say anything about the MAP Sensor.

 

I am reading from a list straight from GM that outlines every single code they put out for all make and models engines from code 12 all the way to code 132. However, I am sure my code is talking about egr functionality because that could very well be the cause of the gas smell.

 

305RSlc

I had the same problem with my '91 Z28 with the rotten egg odor. It also threw a code 32 which is the egr. After replacing the egr the smell disappeard as well as the code 32.

Hope this helps.

Chevypower91

 

when reading those kinds of things, you have to make sure that you are reading the codes that are SPECIFIC to your vehicle. some codes to have multiple definitions, but each definition is for a particular family of vehicles.

 

Yeah, I'm aware of that. It just said MAP sensor circuit but didn't give a definitive engine make that it was going along with. However, I figured out the culprit. Since I had been working on it for nearly 3 months to get it running and fixed up, I over looked the plugs wire locations in my haste to get it on the road. I had 2 plug wires crossed, which made me run on only 6 cylinders. The timing was also WAY off, not sure by how much since I don't have a light, but the guy at the shop reset it for me. Now it idles glass smooth, has AMAZING power, and the raw fuel smell is all but eliminated. I am running a bit rich still, but I think that is due to my o2 sensor being fouled since I was dumping A LOT of raw gas into the headers. Thanks for all the suggestions though guys, greatly appreciate all the help.:hail:

 

Glad to hear you got it all figured out.