I could use some new ideas. Have been fighting with this thing for a while now. Replaced lots off stuff and still have issues. When I have the laptop hooked up with HPTuners it will idle perfect if I add 15* timing. Without that it shakes and idles terrible. Only code is p300.

A little history.

Back in December my wife was driving home from work and it went from running great to really bad all at once. Since then I have either replaced or swapped with a friend's running Blazer the following parts

Injector harness
Timing set (chain/gears)
Coil/ICM
knock sensor
spark plugs/wires
O2 sensors
Crank sensor
MAF
Distributor
Cap/ rotor

All timing marks line up on pulley and distributor. I also moved distrib one tooth forward and back from "6" position. It ran much worse so I am sure the distrib is right. As said before....as soon as I add 14-15* timing the idle smooths out and it runs perfect.

I am at a loss. Myself and a friend that has helped with most of this have worked on cars for quite a while but this.....has kicked our butts. I have searched all over the site and haven't found anything that I haven't done. If anyone has any other ideas please throw them out there.


Thanks!
Jason

 

Have you tried the distributor cap? That turned out to be the P300 problem with my truck a while back. I fought with it for several days before I finally got it figured out.

 

Thanks. I forgot to list that. Cap and rotor too. I replaced so much I lose track!

 

Since I see you replaced the distributor and I see you replaced the CKP sensor did you replace the CMP sensor as well, if you did you may have to check the CKP/CMP correlation values to see if they are within specs.
Best bet is take it to the dealer and tell them you replaced the distributor and tell them you need a case relearn done... if your laptop program is capable of doing that you could possibly do it yourself but do a search and read up on case relearn

 

Yep, I replaced both sensors. Did case relearn as well.

I thought the same thing concerning case relearn. I really would have thought a timing issue would assume crank or cam sensor. No dice there.

I'm wondering if there is a possible PCM issue?

 

Have a read thru this, are you sure both timing marks are lined up correctly and the rotor is in the right place https://blazerforum.com/forum/tech-articles-diy-29/edi-engine-timing-24373/

 

Yep. I actually saw that thread again today and went out to double check. All marks line up.


I really appreciate the quick responses and suggestions.

 

I'm having the same issue with my 2000 S-10 Blazer after installing a motor from a 2000 Bravado. Changed out everything you've changed and no luck. Just today I found out that the Bravado motor runs with a retarded timing for emissions. It uses a different timing chain than mine. I'm hoping it is the problem. Make sure you got the chain that goes to your model, there's more than one, you know the parts stores.

 

OK sorry about your problem I had a code P0300 on my truck and it was a nightmare.You already said you replaced your distributor that was my problem try this pull your cap,, you will have some play up and down on your distributor pull up on the rotor and see if there is any movement back and forth if there is the distributor is bad. Just because it is new does not mean it is good. You said you advanced your timing and it seem to be ok . Your computer on your truck is in charge of advancing your timing on your truck when the engine starts up and running. If your processor is not advancing your timing your truck is going to misfire on all cylinders causing the p0300 code.Hope this helps I feel bad for you and your p0300. I feel your pain. I see you changed something called a ICM,I dont know what that is but if it is the PCM you changed do a crankshaft relearn on it. I have seen you have changed a lot of parts on it but don't forget when you change a part do a relearn on it cant hurt.

 

Double checked distributor. No play. Leaning more towards computer. Hopefully I can find someone close to swap with to see.

Never had a vehicle kick my butt like this!