Hello everyone, first time poster here as I just bought my first Blazer. While I am new to this forum and new to Blazers, I am very familiar with repairing my own vehicles I'm happy to be a part of the forums!

That being said, I just bought a 2000 Blazer ZR2 from a guy at my work who needed it gone, and I picked it up for a low $600. It's from California, so the body is very clean (especially compared to the other Blazers up here in the Detroit area), but it does have a few funny little issues. I HAVE done my research on this forum and it has already helped me out with a few of the issues, but I will still post them along with my main issue as I have a hunch they might be related. Let's get into it.

1. 4x4 not engaging
This forum has already helped me narrow this down to a vacuum leak, I am just waiting for better weather (that's not below zero) to get around to finding the leak.

2. P1870 Transmission slip code
This forum has also helped me narrow this down to either a bad valve in the trans valve body which needs to be bored out, or a vacuum leak. I'm hoping when the leak is found it will fix the issue, as I don't notice the infamous 1-2 hard shift, even after extended highway driving.

3. INTAKE backfire on START ONLY
This one is where I really need some insight from people who may have gone through the same thing. I have searched, and I find people with the same issues, but it seems they either threw parts at it until it stopped, or they failed to update the forum when they found the issue. Here's what's happening for me: I try to start up the truck, sometimes it starts right away with no issues, other times it takes a while and backfires before starting. I know that this true intake backfire can harm intake manifolds and gaskets, as well as a bunch of other things, so I don't push it. Most of the time, intake backfire is a timing issue, however many people on this forum have replaced their distributors, coils, plugs, and has not fixed the issue/they didn't update after fixing. After the vehicle starts, it runs and drives very well with no misfires or backfires, which in my mind would rule out coil/timing/ignition issues.

My question: Has anyone experienced a vacuum leak (because I'm well aware my car has one) that would cause starting issues/rich condition that might lead to unintended off-time combustion resulting in intake backfire? Thank you for bearing with me. As the weather warms up, I will be taking any advice from here into account as I fix her up. I intend to update this thread with my experiences along the way too.

Thanks again.

 

Welcome to the Blazer Forum!!! $600 bucks for a ZR2 is a complete steal You should almost feel guilty lol! I am not very advanced on the types of trouble you are having but rest assured others will jump in and help you out

 

Thank you for the warm welcome! Yeah, I almost felt bad, but the previous owner had it for a decade and just upgraded(?) to a lease last month and it was just sitting, so he just needed it gone. I'm excited to give her the love she deserves!

 

There are quite a few members on here that own ZR2s... Trust me, this forum is super active and these guys are top notch!!! I learn a lot just by reading what they have to say and occasionally I try to help but mostly to no avail It is a tight group as you will see

 

I thought by now you would have had several people giving advice ect... Sorry I can't help but someone out there hopefully will save the day

 

The vehicle is 19 years old now, and I have no record of the distributor cap/rotor being updated, so I am going to first replace those items and see if it makes a difference. As I replace things, I'll be narrowing down the possible issues and I'll update the thread as I go so that if anybody ever has the same issue I will have possible solutions recorded. Check back!

 

Alright everyone, just an update as promised so there's a record of what may be a fix for this issue... I replaced the distributor cap and rotor yesterday (it was finally warm enough in Detroit at a balmy 39 degrees F), and while I was in there, I happened upon the vacuum leak incidentally. It's a severed vacuum line (looked cut) that went from under the battery (4x4 probably) over the motor and behind. I'll track down the other part of the severed line tonight and see if I can replace it quickly. While I was doing the cap and rotor, I also cleaned the MAF sensors, which seemed a little dirty, but looked in otherwise good shape considering the intake backfires. When I took it on a test drive it started fine, but hesitated just a little on startup. No backfire, bu that didn't happen every time anyway. Hopefully the distributor got rid of that issue, the terminals on the old cap were pretty burnt. Tonight I'm going to clean out the throttle body and track down/replace that vacuum line if the temperature stays over freezing. This weekend I might throw some new spark plugs and fuel filter in if I get the time too. I'll keep updating until I'm sure the issue is resolved. Hopefully this will help someone down the line.

 

I hope it all works out for you... I am shocked nobody else has responded though...

 

All of your accessory, 4WD, transfer case, HVAC are run from a single port on the intake manifold.
Here is a link that might help



https://blazerforum.com/forum/2nd-ge...vacuum+diagram

 

Thank you very much for the information. I will update tomorrow when I get the line replaced!