96 blazer gets hot and quits

[malkab]

Ok, my 1996 blazer is being a total nightmare. I do not have the best mechanic I know, but I am on a very strict budget and he is cheap and has the necessay tools to fix the problem, my hands are bound a better mechanic is out of the picture so don't even suggest it. Ok, Next because I've read several of these and I know what questions to expect.

Truck is CSFI, yeah i know . Fuel pressure is fine, gauge has been put on it and it's ok. The fuel pressure has been checked at every aspect possible, and though i can't remember the exact PSI, I know it was enough to start the truck and keep it going (upper 60s low 70s psi). The fuel pump psi has been checked before and after startup, to after it quit, to it being stopped and just turning the key to the RUN position. Plus it has a brand new fuel pump, and a new fuel filter. My mechanic states that it is a spark issue. So far my mechanic has replaced crank sensor/ignition module/the computer/map sensor/distributor/some ignition thing on the steering column.. idk?/ Spark plugs are new enough to not be bad, and plug wires may be kind of old. I don't know about the EGR valves or anything like that. My mechanic thinks the only thing left would be the Mass air flow sensor, but I don't think that is it.

Could it be the fuel relay switch? I'm not sure if he changed the cam sensor either?

As far as symptons: The truck hesitates after it has been running at operating temperature for a short period of time, normally less than 15minutes. It seems to mainly hesitate when I come to stop signs and stop lights and then try to take back off again. The truck will eventually quit on me. It always starts right back up after it cools off though, and while it is cool it runs great! Has 139,000 - miles

Ok, I think ive covered most of the bases so hopefully the next reply can be straight to the point and not asking me some more questions about whether this or that has been done. Anyway, please advise. THANK YOU

[Chris Stewart]

Does the Check Engine light come on? Do you know of any trouble codes?

[malkab]

No SES/check engine light, no codes in memory. The more Ive been thinking about it and from what I have learned from this forum about how the ignition on these 96' blazers are controlled, I'm starting to think it may be the CAM sensor since it controls timing. When the blazer hesitates and you push on the gas pedal it will backfire, backfiring is an indication of timigng issues, right? Could it be possible that the cam sensor is maybe shorting out when it get's hot? Also, where is the cam sensor located?, and does anyone know a ball-park figure of how much they cost?

[AJT1961]

Bad ignition wires can work fine when they are cold, fail when they get hot, and then work again when they cool off. This can cause the symptoms you describe, particularly when the bad wire is the one that goes from the coil to the distributor cap. This should throw a multiple random misfire code though, so you may want to double-check with your mechanic about there not being any codes.

[malkab]

could there be a trouble code in memory with the SES light off?

[Chris Stewart]

There could be a pending code, just on the edge of setting a code. Does the check engine light come on when you first turn the keyswitch on in bulb check?
Most chain type auto parts stores give free scans.

With it running fine cold then running poor at normal temperatures make me wonder if it's something in Closed Loop, possibly de-fueling to satisfy O2 sensor/computer parameters...time for the Pros.

[malkab]

When I turn the key forward to the RUN position the SES light is on.

Im going to try spark plug wires next to see if that works. The reason im stuck to this mechanic and not a very good one is because I'm not the one paying for it. I'm a poor college kid and my parents are refusing to pay too much for it. If the repair bill even get's up too high they have already told me they won't cover it. They just paid for a fuel pump for it not too long ago, and they fear if they pay too much for it again, then something will just act up on it again and they will just keep to having to put more and more money into it. I swear the next vehicle I'm buying will be a toyota.

Also, I don't know if this helps, but about a year ago maybe, maybe a little less the SES light came on. I had it scanned and it was an O2 sensor the guy told me, said it was the second one on the left bank or something. Not too long after that the SES light went off and stayed off so I never did anything about it.

I really appreciate any and all help and advice on this. I need all the help I can get.

[emt1134]

These motors are known for problems with the spider assembly. The poppet nozzles clog up. Although you may have good fuel pressure at the main line, you need to see if fuel is have trouble getting through the individual nozzles. Does this guy have access to a Snap-On scanner ? You need to check your computer for history codes and data parameters.

[malkab]

Not sure if he has a snap-on scanner, I'll ask him soon. Could you please eloboarte on "poppet nozzles" are, and what a "spider assembly" is?

The last time I talked to my mechanic he said he was going to do everything he could to check the computer out thorougly, and was going to try to make it fail so the SES light would come on. The whole time it's been acting up, which has been for about 2 months now the SES light only came on one time, and that was when I was driving down the highway with it, I slowed down for traffic in front of me and when I pressed the gas pedal after the vehicle in front me turned off, the truck fell on it's face, but it kept going. I was holding the pedal to the floor and it was taking everything it could to keep it going 50mph, it stayed like this for a few miles and during this longer period of time while it was acting up the SES light popped on. It was evening time so I drove it to my mechanic (he was closed), but my dad had to drive it again later when it cooled off and he said while he was driving it, the SES light went back off so my mechanic never had a chance to scan while the light was on.

[emt1134]

It doesn't matter if the light is off. The code is still stored in the computers history. Tell him to scan it and see what codes are there. Don't forget to write them down. Also, when the light was present, was it constantly illuminated, or was it flashing ?

[malkab]

The light stayed constantly on. Also, the computer has been taken out, could the computer being disconnected from power cause it's memory to be erased?

[emt1134]

so the computer was replaced ? if so, has the check engine light come on since it has been ?

[malkab]

No, the light hasn't come on since it has been replaced. When the new computer didn't fix the problem it was swapped back for the original. I talked to my mechanic today and he said he couldn't find any codes in it's history/memory.

[Chris Stewart]

Have heard of trash clogging the pickup screen in the gas tank on cars all my life but I haven't actually seen it yet BUT, with all the trouble you're having, keeping a fuel pressure checking kit in the car (available on sale at Harbor Freight <$20 and <$40 at most chain type auto parts stores) will let you check the fuel pressure WHEN the motor is having a quit event so you'll at least know whether it's a fuel issue when it quits. Carrying a new spare sparkplug so you check spark at the time of failure will also give you good info when the motor quits running.

Here's where you check the fuel pressure.

[malkab]

Well, It seems as though my problem being fixed was too good to be true. Of course this couldn't be that easy. Well, replacing the plug wires and the blazer running good was merely coincidental, it ran good all weekend, but the temperature was cool, about 55-68 degrees. Today, drove to the store, it was about 80 degrees out, it started hesitating again and then quit on me. I pulled over, waited about 10 minutes, started it back up and took back off again and made it back to my house. Not sure what to do next but I think im going to change all the O2 sensors, I just got under it and noticed 3 of them, but I think there is 4. I asked the guy at Advance Auto parts to quote me prices on the O2 sensors, he told me that it only took two of them, but I can see more than two? Their prices where 52.98ea.

I took my ignition module to Advance auto parts today to have them test it just to make sure when I replaced it the one I replaced it with wasn't a lemon. Well it turns out my ignition module is 4 prong connecter and they didn't have a 4 prong connecter to fit to it. So much for that. Even had the guy scan my computer even though the SES light wasn't on. He said all the saw was an O2 sensor in it's memory and that was it.

Also, don't know if this would make a difference but I thought I would mention it. I put a K&N short ram air intake on my blazer with an open cone filter, to help it out a little bit with gas mileage. It has been on my blazer for at least two years.

Thanks for the picture Chris. I wasn't sure where to check the pressure at. My grandpa used to be a mechanic, too bad he died, but I know he has a fuel pressure gauge somewhere. My dad would probably know where it's at. I'm going to get a spark plug and a fuel pressure gauge just like you said, that's a terrific idea.