ok i just got a 86 300E and it has a rough idle. i searched the forums and i think i narrowed it down to the maf. i found one for 100$ with a six month warranty, but before i get it i want to make sure that its causing my problem. this is what it is doing...
hard starts... did a starter draw test and checked batt feed circuit checked out ok
idle smooths out at about 1200 rpm and only idles rough in a drive position
tranny shifts are hard and long (vacuum modulator???)
ecomomy gauge at idle is in the red (i have low vac at idle)
hesitation on acceleration from a stop
12 MPG!!!!

what i need to know is, are these common symptoms for a bad maf? from what i have read, yes but i want a second opinion
i would also like to know what the normal values it sould be reading so i can test it, is the maf a 5v feed? if so WOT should be near 5v and idle would be around 1v.
any help would be great thanks

 

Honestly I would look for a large Vacuum leak. That alone would throw all your reading off and cause the tranny to shift hard.


Brian

 

Yeah it sounds like the vacuum leak is really your problem rather than the low vacuum being a symptom. A vacuum leak will cause rough idle, slow transmission shifting, poor running in general, etc. Carefully examine all your vacuum lines and where they connect to your various intakes into the manifold and "T" connectors. A good way to find a vacuum leak is to take a butane/propane torch (those bottle types you use for plumbing or one of the small handheld kinds from radio shack) and turn on the gas (BUT DO NOT LIGHT IT!!!) ever so SLIGHTLY and hold it near and run it along all your vacuum lines and connections. If you come near a vacuum leak, your idle will increase. REMEMBER DO NOT LIGHT THE TORCH AND CREATE NO SPARKS AS YOU ARE DOING THIS I do not take any responsibility for my advice if you blow yourself up :p However, this is a sure way to find even the smallest leak. If you dont have a torch then move the lines around by hand as you examine them to find broken hoses or broken brittle connectors. Good luck!

 

MAF problems normally relate to the later multi valve engines with HFM electronics. I don't think MAF failure is common on the 300E.

 

Yes everything mentioned in the problem comes back to a source that used a type of Vacuum. These cars it may be hard to find but you may have a $1.00 problem over a hundred. The pocedure rcltrh mentioned is excellent and can track down a problem your eyes can't see.

Brian

 

you guys are awsome thanks for all the advice i will let you know how it goes
i am a student at wyotech in west sacramento (so im poor) and vacuum line is a whole lot cheeper than a MAF

i got one more question i know that the early 124s have the SOHC and that the newer ones have a DOHC 24 valve, so my question is are the heads interchangeable?? (i heard that they were from a teacher) if so what are some things to look out for? it would suck if i mashed some valves. but i would love the increase in HP