Air Flow Meter Failure??

[besweder]

Greetings, very fresh Newbie here. My '92 FJ80 has developed an erratic, nasty stutter/choking action that felt like a bad miss at first. I took it to the local dealer where the mechanic diagnosed it as a bad air flow meter. The service rep wanted to replace it to the tune of over $1K, but the mechanic said he'd had success cutting them open and cleaning the connections, hopefully saving 80%. Well, he did it, but it made no difference. I took it home and did a resistence check with guidance from my Toyota Repair Manual. All of the resistance was within spec. Now I'm stumped. Has anyone had this problem? Do you think the mechanic was on target? If not, what else does it suggest? If so, do I really have to spring for a new unit from Toyota? SOR listed a used one for $300 & a local recycler had a line on a couple for even less. Don't want to waste my $$, but I'm not sure whether to trust a "used" electronic part.

Thanks for any help you can give me. Glad I found this BB. BTW, I did check the FAQ & search function, but didn't find anything real close to these syptoms.

 

[landtank]

I'd check the black ribbed tube that goes from the air filter over to the Throttle body for cracks in the pleating. This is a very common problem and gives you an engine that runs as you state. The other option if you have an accompanying CEL is the wiring harness at the EGR valve. The harness over there gets hot and the wires can short together resulting in a CEL.

 

[besweder]

No CEL

Thanks for the suggestions. There are no apparent cracks in the ribbed tube. I'll try to check EGR wire harness tonight. The CEL hasn't come on at any time through this problem.

 

[CJF]

BTW, I did check the FAQ & search function, but didn't find anything real close to these syptoms.

What symptoms? You didn't describe yours in much detail. Does it happen evey time you drive it? at what rpm's? only when warm? etc...

Also, what maintenance has been performed recently and can therefore (probably) be ruled out? Spark plugs? wires? fuel filter? And if so, were OEM parts used?

Since you have the manual and are handy enough to check the AFM yourself, why not keep it away from the profe$$ional$ for a while and figure it out on your own? For example, look at the troubleshooting section starting on page EM-5; that should give you plenty of ideas, and we will too if you give us more information.

Welcome,

Curtis

 

[psfpilot]

Have you checked all the vacuum hoses? A vacuum leak can cause extremely rough running, particularly at idle.

As Curtis said, it would be helpful to describe the symptoms and the parameters of their occurence with more detail in the interest of more accurate diagnosis.

 

[cruiserdan]

I'd check the black ribbed tube that goes from the air filter over to the Throttle body for cracks in the pleating. This is a very common problem and gives you an engine that runs as you state.

That's my bet.

 

[nelsongarcia3]

you heva to check temperature sensor if is ok or not

 

[Biff]

Don't buy it from SOR, I got a good used one from a local junk yard for $160

 

[besweder]

Most recent service: ~5-6k mi. and 12 months ago: 30k Toyota service w/ new filters, fluids, plugs, etc. plus new distrib. cap & rotor & new plug wires. New alternator ~4k mi. ago.

Truck has had an occasional, slight miss for awhile. Last week, after ~65 miles at 80-85 mph on I-25, nearing home, it started to intermittently chug & felt like a bad missfire. It generally starts OK, but returns to rough running after a short time. It runs rough at idle, nearly dying after sitting at idle for a few minutes. It will smooth out by cranking up the RPMs, although it may just be the added speed smoothing over the rough spots. It is driveable, the roughness seems to happen mostly on startup from a stop and at moderate engine speeds, but can happen any time. There is no discernible affect on temperature level.

The mechanic said he could get it to run smoothly by sticking a long screw driver in through the air intake an nudging the measuring plate in the air flow meter (AFM). He said fuel pressure is good ~42 psi.

I'm talking to my local recycler about a used AFM, but my question is, if all the resistence readings are in spec, can the AFM still be bad?

I've checked the ribbed black tube and found no indication of cracking or leaking. I've attempted to find vacuum leaks, but haven't discovered any yet. Any suggestions on how to search them thoroughly? Or any particular ones to check? The engine compartment on these things looks like a snake pit of tubes & wires.

One final thing in the interest of full disclosure, the exhaust system has been rattling for many months (Catalytic converter?). It seems unlikely to me that this would suddenly be affecting driveability? But, I'm no expert.