Hesistation in my 262, 95 Blazer OBD II

firecadet613 · September 13, 2004

I've got a late build 95 Blazer, that has the OBD II. Here's my problem. With the EGR valve plugged in, no SES light is shown, but there is a hesitation and torque convertor lockup does not occur. It idles fine, but as your accelerating there is a bad hesistation from 1500-2500 RPM's. Right now I have the EGR valve unplugged and it runs perfect, torque convertor locks up when it should, no hesistation, the only problem is the SES light is on do to the EGR valve being unplugged. This is the third EGR valve, I've returned two new ones within a few days, so that rules out it being a bad EGR valve. Wiring looks good, so I am thinking it's a sensor tied into the EGR circuit? Could it be a MAP sensor. I'd rather not go into this blind throwing money at parts I do not need, what gets me is it runs perfect without the EGR plugged in....

Any ideas?

Joe

o4yukonxl · September 14, 2004

These engines are famous for getting carbon build up under the EGR valve, which plugs the EGR input. I had this problem on my 93 4.3 and had to remove the EGR and the upper intake to clean out the EGR port.

firecadet613 · September 14, 2004

There is no carbon at all in my engine currently....

millerwd · September 14, 2004

well it's not the EGR!

you've triied 2 of those.

The EGR is acuated based on MAP and RPM data.

so what possibilities have we got:

1. bad wiring to EGR

2. Faulty MAP, seems to me you'd have additional problems.

3. RPM values are corrupt in ECM, dealer would need to reflash ECM.

4. the missing link., the thing we haven't identified

let us know what the fix is ok.

billm

firecadet613 · September 14, 2004

New MAP sensor did nothing.

02denali · September 14, 2004

i think the valve is stuck. it might be allowing air in there that is not needed. when you unplug it it takes it out of the loop.

firecadet613 · September 15, 2004

Looks like the new TPS I put on two months ago was bad, put a new one on and seems ok, will report back in the AM for sure.

Joe

firecadet613 · September 15, 2004

SES light came back on, I'm guessing its P1406 again, what should I be looking for? EGR valve is new and wiring is ok, TPS is new and MAP sensor is good...

Joe

95Blaze · September 17, 2004

I hear you loud and clear Firecadet613!

I got the same blazer. The same problem has pleaged me for over a year. The problem is the tiny carbon particles that get stuck in the EGR valve causing a minor leak resulting in engine miss. To a much bigger pieces of carbon that will hold the EGR valve way open, causing major engin miss and worse of all so much vacume is lost there is not enough to power the Power Brakes! NOT COOL!

What I've tried so far was first removing the EGR and shaking out the carbon particles. Then use a shop Vac to suck out what I could from the lower Intake that was a breif fix.

Then the guys on S10fourm.com suggested that I try using Sea Foam. By running the engine at idle and pouring the Sea Foam in the Brake Vacum hose slowly using about half the can. Then let the engine sit for a 1/2 hour and then run it til the blue smoke stops coming out of the exhaust. Still did not fix the problem returned in a couple of weeks. But I did gain a smoother acceleration.

Last attempt. This weekend with the engine off, I drained the oil I tried using the Sea Foam spray and spraying the lower port where the EGR bolts to (where all the carbon come from) and used about half the can. I was expecting the Sea Foam to work its way into the oil pan and drain, but it never did. I let it sit for a half hour or so, then refilled it with the oil I drained and tried to start it. Well the engine would not turn just click. I thought maybe I hydro locked the engine or something like that but on the fifth try it started. Then the blue some appears. After a half hour of paining my neighborhood blue I took it to the freeway. I was embarassed for little while til I got it all burned up on the freeway. It clear up pretty quick after that.

Well this week the engine stumbled one, the SES light turned on but then after a hard acceleration it smooted out. The the next day the SES light turned off. Well at least it saved me the trouble of connecting my Auto X-Ray to clear the code AGAIN. and it has been fine so far.

I don't know If spraying the lower intake directly like I did is advisable but I was not in the mood to remove the plenum again. I already fixed the leaking CPI. If it happens again I'm gonna drive it off a cliff. Or trade it in.

firecadet613 · September 18, 2004

My EGR is OK, I think it might be the TPS or another sensor...

95Blaze · September 20, 2004

My EGR works too. The problem is the carbon that gets stuck in the valve opening and keeps it slightly open.

Does the Blazer run alright immediatley after you re-install the clean EGR, then start to have problems soon after? If so then it sounds like carbon. Try running with the EGR disconnected after you clean the EGR once more. The purpose is to keep the EGR closed and prevent carbon from being sucked in, causing the valve to get stuck open. The SES light will stay on While it is disconnected.

Just a tought.

firecadet613 · September 21, 2004

Thanks for the idea...no carbon though!!! I wish it was simple lol

Jerther · May 31, 2005

I'm having almost the same problem.. the difference is that the engine keeps missing even if the EGR valve is unplugged. I also tried to plug a screw on the valve end of the tube and nothing changed.

The Service Engine Soon light goes on when the Valve is unplugged.

It is not always happening. Sometimes, the engine runs like a beast! I have not found the conditions when it runs so well and it has been happening for almost a year now...

BTW I've got a 5 manual so I don'T have that torque converter prob...

I'll get another valve and see what happens, in case my current valve did not close correctly.

I tested my TPS with a ohm meter and it seems ok (5 KOhms max and seems smooth)

MrStaggrLee · May 31, 2005

One solution to EGRs hanging up from carbon particles on the 4.3L CPI with the linear EGR valve involves installing a gasket with a fine screen built in. Im not sure who makes them at the moment but I'll check in the AM for a part # and source.

Jerther · June 1, 2005

changed the TPS. no change.

Changed EGR valve. no change.

And i've been told that a faulty MAP sensor would make a code show up. And there is no code in the computer.

I noticed that when the hesitation appears, i run the engine on high RPM for a couple of seconds and the hesitation stops... for a couple of minutes..

I remember trying some injector cleaner and having good results. I'll try it once again and see what happens.

Then the next step would be to test the gaz pressure.

Here's another hint. The hesitation also appears on high rpms. I don't have a RPM meter so by high rpm i mean higher that I usualy reach at normal driving.

It's kind of weird...