Would having one cylinder with the compression down 30 to 40 lbs compared to the other five cause the check engine light to be set on a
1998 Plymouth Grand Voyager minivan with the 3.0L V-6? I can't find anything else wrong. The mechanic is hesitant to do a valve job becasue he claims he has seen this before and fixing the compression did not fix the problem (and turn out the check engine light). He recommended dumping the van and buying something from another manufacturer (Ford, Toyota, GM, anything but another Chrysler product). I really trust this mechanic, so don't say he is a moron.
Misfire cylinder #5 (P0305). This code comes up consistently. I have been fighting this problem for months. Many things that have been done - Plugs (three times - the dealer, Western Auto and me) and wires (twice once at Western Auto and once by me), distributor cap, intake manifold gaskets replaced, swapped injectors around (misfire stayed the same), O2 sensor (old one looked bad on the diagnostic scan but there was no code), fuel filter (needed one). At first the light came on occasionally and sometimes went out by itself. Later, after I reset it, it would stay out from 1 day to 2 weeks. Now it comes on after a few miles. The mechanic is concerned that he will be able to fix the low compression, but not fix the light. He has had similar symptoms on two other mini vans with this same problem. In both cases he did a valve job and restored the compression, but the light kept returning despite an engine that seemed to be running perfectly. In my case, the problem is always the same (#5 misfire). The van runs OK and has about as much power as it ever had. I told the mechanic to do the valve job. I think he is worried it won't fix the problem and I will be mad at him. I think it will fix the problem and I won't be mad at him even if it doesn't. I think a cylinder that is 40 lb. less than normal (160 lb. or so) is out of spec. I was taught that the low cylinder needs to be within 75% of the high cylinder. This is engine is out of that range. Since I told him to just do it. I guess I'll know if the problem is solved soon enough.
This is like deja-vue. I've had 2 of these in the shop in the last few months. As much as your mechanic doesn't want to, pull the heads and do a valve job. Be sure to check the guides for any wear. I'll even go a can of Mug rootbeer that it fixes it...
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