I got a weird issue that I can't seem to correct. Truck runs great off idle, no hesitation, no misfire, nothing. After it has been running for about 5 mins or so the idle at lights, parked etc. every few seconds just drops like half the engine cuts out. I have checked all the usual suspects, egr, tps, iac, map, they are all fine, replaced them regardless but am still having the same problem. Fuel pressure checks out at 55psi steady, no drop once shut off. Did a tune up ( plugs, wires, cap and rotor) that made no difference. There is no codes right now, there was a code 43 for a while but has gone away. I am at my wits end with this I am just out of ideas. Any help would be appreciated.

 

Well it just died for the first time. Started right back up with no problem. I will say the problem is worse while in park than when its in gear. Maybe its having a problem when it goes into closed loop, I say that because if it sits for a few minutes the idle is good for a little bit then goes haywire.

 

I sure as hell hope you figure it out before I go broke trying to figure out the same thing on my 97 S-10 P/U 4.3.

I bought this truck for $1.200 and thought I got a good deal but now I'm having second thoughts.

Symptoms: Bad Hesitation off idle and even back fires if I give it 3/4 or full throttle.
Otherwise it starts right up and idles smooth as brand new.

As soon as I start it,,, it has good response but after it runs for a minute or two it acts like it loses fuel pressure but the pressure is still around 55-57 PSI engine at idle and 60-62 PSI key on engine off. I changed the fuel pump twice to make sure this wasn't the problem unless I got two bad fuel pumps in a row. I have ruled out vaccuum leaks.

Keep in mind; I AM GETTING NO OBD CODES / NO CHECK ENGINE LIGHT

PLEASE READ THE FOLLOWING BEFORE LEAVING A REPLY;
I know theres a lot of threads on this issue but none of them have fixed the problem with what I've done so far or they never followed up with the the solution.


This is what I have replaced so far and still counting:

· Fuel Pump (Twice)
· Fuel Pressure Regulator
· Fuel Filter
· Fuel Injection Spider
· (TPS) Throttle Position Sensor
· (IAC) Idle Air Control Valve
· (MAP) Manifold Absolute Pressure Sensor
· (CPS) Camshaft Position Sensor
· EGR Valve
· Catalytic Converter
· O2 Sensors (Front and Back)
· Purge Valve
· Distributor Cap
· Rotor Button
· Spark Plag Wires
· Spark Plugs

Now I'm thinking the (MAF) Mass Airflow Sensor but when I unplug it, the Check Engine Light comes on so that tells me it's working properly.

I'm about to set fire to this MF'er and be done with it.
The local shops are IDIOTS, they say there’s nothing they can do without the Check Engine Light being on,,, well DUH,, If that was on I could fix the damn thing myself so that just tells me these guys don’t know how to use their equipment.

My next option is to buy the software program and cable off ebay for $80 and diagnose it myself.

If anybody out there can help with this issue, I would really appreciate it.
I do have other transportation but I’m tired of spending every weekend under the hood of this evil POS.

Thanks in advance.

 

patrick 55 psi is too low if thats at key on. Needs to be around 60. Yea,a few psi makes a difference.

Viper. what brand pumps are you buying? If its anything but ac delco it may be your problem as aftermarket pumps seem to be a big hit or miss in these blazers. I went through a bunch of them until i finally got my ac delco and no issues since.

If you turn the key on,and the pressure goes up to 60ish,but then slowly falls a good bit in 10 min,its either your spider,or check valve in pump...Im betting its the spider as they are a known accurance for going out in cpi engines (well,leaking out the regulator hole). Pumps seem to either just quit or get weak.

 

Chris015,
The fuel pump is AC Delco, thats why I changed it twice.
The first one was after market but it still had the same pressure as the new AC Delco so it was working right.
The spider was the original one that came out of it, I sent it off to be rebuilt and reinstalled.

I forgot to mention above; I replaced the ECM with a known good one and it didn't make any difference.

The problem was the same before and after changing the parts listed in my original post above.

Oh yeah,,,MPatrick,, I'm not trying to highjack your post, I'm just thinking we both could have the same problem and I can save you a lot of trouble by showing you what I've done so far and still haven't fixed the problem.

 

IAT Intake Air Temp? Does a '93 have such a creature?
I was thinking MAF & CAT... they're OK when cold but when they warm up they stumble & or stall. What effects an engine when it gets warm? - air intake temp (not adjusting for the warmer engine) & the CAT & O2 sensors.
When things warm up they expand/get loose. What can be moving that tiny bit that'll make a difference? A vacuum line, rotor, cap, manifold gaskets?!
Just thinking outloud.

 

Rotti,

Your 93 does have a IAT Sensor.
It should be located in the Breather Duct between the breather/filter and the throttle body about 4 inches from the MAF.

 

Thanks viper but I was replying to the OP lol... Either way at least we know there is one & I'd look at IAT & see if it's working properly/hooked up.