Only way to find out is by looking at your air intake tube between air filter box and throttle body. MAF sensor is mounted between air filter box and throttle body. MAF sensor can have 4 or 5 wires.

 

If it looks like this, then I guess I have one. I cleaned it and did the checks on the 02 sensor. Sensor reads good and cleaning MAF did no good. Really disappointing...Don't know where to go from here. Guess I'll leave the 02 disconnected until I can figure it out. At least I can drive it. Any other things to check? Thanks for the help so far..BTW-My Haynes Manual makes no reference to the MAF sensor. That seems odd....




Rick

 

BTW-What is this one??

 

Yes, that's MAF sensor.

did you disconnected battery for more than 10 minutes and recheck for codes once the engine warms up?

You have to drive your truck for couple miles to re-learn EEC IV programming.

Posted back...I can give you step by step MAF procedure as long you have the codes for MAF coming back on.

edit::: please do not leave HEGO sensor disconnected. This will throw off any diagnosis procedures.

 

That's ACT sensor.
stands for air charge temp sensor.

 

I disconnected the battery when I started working on the MAF. Took me about an hour, with letting it dry out and all. I did drive the truck for a few miles, but with it bogging down, that's about all I could handle. It's getting worse everyday. I have not checked the codes yet, but I will today. I'll reconnect the 02, also....Thanks for the help....


Rick

 

I went over your post twice.

I notice something.

Have you check your fuel pump pressure?

Low fuel pressure will submit HEGO codes.

It is free check and it doesn't cost you $$$

 

OK. This is what I got this time. Remember I had the 02 sensor unplugged after clearing the codes, so I expected the 172 code. As for the EGR, it was clogged up before and I freed it up(Read post up above). But one thing I did notice, is that when you pop the throttle, it doesn't move like every other car I've worked on before. Related to that, is the fact that I don't think I'm getting a good vacuum to it. The reason I say this is, I removed the black vacuum line from the EVR and applied direct engine vacuum from an unused port on the engine. Then it popped open like it should when I popped the throttle open. I should have mentioned this before, but I really thought something else might control vacuum to the EVR. But as I read the Manual further, it says that the black line to the EVR will ALWAYS have vacuum. It does not on mine...So what do you think now?
111
172
332

Nope. Didn't check fuel pressure. How do I do that?

Thanks, Rick

Another thought related to the fuel pressure. Would the truck run good, even though it had low fuel pressure, when the 02 sensor is disconnected? I would think if I had low pressure, disconnecting the 02 sensor wouldn't matter. It would still starve for fuel, wouldn't it? I don't know....This thing is about to beat me and I can feel the money flying out the window at the service dept......AARRGGGHH

 

Yes the black vacuum line should have vacuum on it at all times. See if your vacuum reservoir (the coffee can) has vacuum from the red vacuum line.

Sounds like you may have a vacuum leak and when you unplug the O2 and it goes into the Rich Mode it will run better with the vacuum leak.

Here is a diagram.

 

Thanks, Subford

Exactly what I thought. But it appears that there is no leak that is obvious. I took all the "wrapping" off of the vacuum lines and went over them with a fine toothed comb. Could one of those selonoids before the EVR be bad and leaking?Yes, I do have good vacuum at the can. It seems to lose it at those 2 "Selonoids" before the EVR valve, if that makes sense. Not sure what to do about that. When I did hook vacuum directly up to the EVR valve and the EGR appeared to be funtioning properly, it still made no difference in the bad running. What do those 2 selonoids do anyway? Stumped again..............

EDIT:

 

Secondary Air Injection (AIR) System

The Secondary Air Injection system is utilized in electronic control systems to divert secondary air either upstream to the exhaust manifold check valve or downstream to the rear section check valve and catalyst. The system will also dump secondary air to the atmosphere during some operating modes.

A Secondary Air Injection Diverter (AIRD) valve (9F491) is used to direct the air either upstream or downstream. A Secondary Air Injection Bypass (AIRB) valve (9B289) is used to dump air to the atmosphere.

 

Here is a Diagram

 

Is it possible for these to leak and cause a loss of vacuum at the EVR? Man, I don't know how you guys keep up on all this info. Boggles my mind just trying to keep up with the answers....Any ideas where I should head now?

 

I feel like I'm getting off track here with what might be the real problem. Or maybe I'm just not understanding all this emission stuff. Should I now focus on the vacuum problem or keep heading in the direction of parts being the problem? Thanks for your help, Subford. I really appreciate it and I'm trying to keep up.. Any help is wecome....

 

The AIRD and the AIR B Sol. Valves can have big vacuum leaks as they have a job in venting the AIRB and AIRD valves to release them from vacuum.

You do need to make sure you have good vacuum with no leaks for the engine to run right. You can try plugging (bypassing) these two Sol. Valves and run the vacuum just to the EVR Sol. Valve. Then we can work on the other problem and when you get that fixed you can get back to these AIR Sol. Valves.