What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

TBI power loss, exhaust pops

Liberator

Liberator

1/2 ton status
Joined
Jul 16, 2001
Posts
289
Reaction score
0
Location
TX
I've been dealing with this issue for a few years now. It's getting to the point that I can't get very far down the road (14 miles today) without this problem showing up. I couldn't find anything helpful in a post search.

As I'm driving down the highway the engine suddenly loses power and starts popping out the exhaust. It will idle normally but start popping when the engine rpm increases. After limping along the shoulder with the engine close to idle rpm, it eventually clears up.

It's a 1987 K5, TBI 350, 700R4, 100,000 miles. I have changed the following parts chasing this problem:
distributor cap and rotor
spark plugs and wires
ignition control module
ignition coil
map sensor
egr
egr solenoid
spark controller
timing chain has about 20,000 miles on it.
the distributor is tightly clamped

It's almost as though I'm completely losing advance timing. But I'm not sure. I've never had a timing light on it when this problem comes up. I also notice the exhaust gets louder just before it loses power and starts popping. Any help is greatly appreciated. This is my primary transportation.
 
Does it still have a catalitic converter on it ?...seen some become plugged with floating debris from the catalyst intermittently and cause similar symptoms..(and set no codes)..

Might be an exhaust have sticking open when it gets hot,then after it cools down some it starts opening & closing properly..

Might check the fuel pressure too,if you could drive it with a gauge hooked up that would help determine if the pump is crapping out --running lean can cause backfires and gets the valves red hot..usually that will set a check engine light code though..
 
Thanks for the reply. The Cat is fairly new, replaced a few years ago with the muffler. As for an exhaust valve sticking, I could understand that for an engine stumble. But this is a complete loss in all cylinders. If I give it more accelerator it will shut down completely. It will only idle in this condition. I'm not sure about the lean condition. If I stay on the accelerator, I can make it pop like hell! That's how I let other drivers know I'm having trouble and moving to the shoulder. Everyone on the road makes evasive maneuvers to get away from me.

Is there anything else it can be? Is there anything that would cause me to lose advance timing? If an exhaust valve is sticking, will it affect the other cylinders by way of the ignition/timing circuit? I just replaced the egr and solenoid and I'm still getting a code 32.
 
Kain said:
pull the valve covers and take a look
Click to expand...
Thanks. I'm going to continue with the electronic route at this point since the engine idles normally and a shut-down of all cylinders is involved. Could a bad distributor be causing this? How about a faulty throttle position sensor? I'm not sure what else I can look for. Any more suggestions?
 
what i used to do is pull the valve covers and watch the rockers as its running and see if you have one not doing its thing ,yes it makes a mess but checking to see if you got a bad cam lobe is easier this way, only other way i know to check cam is pull intake and look at lifters or pull the cam
 
A bad cam is always bad, it's not an intermittent problem like this sounds like...

...and there is no reason to run it with the valve covers off. A bad cam will present with a very loose rocker where the bad lobe is. I haven't seen many bad cams since the late 70's small blocks when GM had a bad run of them.
 
Oh yeah, one thing I have noticed to be a common problem on the TBI 350's is the distributor. They self destruct and turn to dust. I have personally seen a few first hand, plus several CK5 members, compared to never seeing a large cap HEI distributor fail. I'd say, remove the cap, rotor and do a thorough inspection. Failing distributors are full of rusty looking dust...
 
The distributor is original. It's probably good to replace it anyway. I was thinking a DUI 12620BK. I replaced the throttle position sensor and the map sensor today. Apparently I never changed the map sensor. It was the original GM equipment. I'm not sure if the map sensor or tps has anything to do with electronic advance timing. The real test will be getting it on the highway and seeing if I can make it to my sister's house 50 miles away. Anytime I try to drive the Blazer to her house, it craps out. Hopefully the map and tps replacement today will clear this up. If not, the distributor and ECM is all that's left to replace. I'm running out of options.
 
Liberator said:
The distributor is original. It's probably good to replace it anyway. I was thinking a DUI 12620BK. I replaced the throttle position sensor and the map sensor today. Apparently I never changed the map sensor. It was the original GM equipment. I'm not sure if the map sensor or tps has anything to do with electronic advance timing. The real test will be getting it on the highway and seeing if I can make it to my sister's house 50 miles away. Anytime I try to drive the Blazer to her house, it craps out. Hopefully the map and tps replacement today will clear this up. If not, the distributor and ECM is all that's left to replace. I'm running out of options.
Click to expand...

Could just be the pickup coil overheating?
 
If the dizzy checks out, or if you swap it out and still have this issue, you may want to do a pressure test on your fuel pump. This could be the result of a bunch of other malfunctioning systems, but it sounds to me like you may have a weak pump or clogged fuel filter causing it to run lean when you get up in the RPM range.
 
I have two references to an injector dizzy and I have no idea what that is! As for the fuel filter, it's fairly new too. I've experienced a clogged fuel filter before but this problem happens right above idle and eventually goes away. It doesn't act like it's starving. I miss my '81 with the Q-Jet!
 
Here is a bit of a writeup on code 32: http://www.chevytalk.org/fusionbb/showtopic.php?tid/258416

The manuals linked in my signature will contain the code 32 diagnosis and explanation of the circuit.

I would suggest not throwing anymore parts at it. Code 32 is telling you which circuit is seeing an issue, you need to use the manual to run down the flowchart. EGR's are notorious for being "wrong" coming from the aftermarket.

EGR introduces inert gas (doesn't provide oxygen to burn fuel), which under anything other than proper conditions, will cause all sorts of issues.
 
Just an update. I replaced the map sensor and throttle position sensor at the same time. The engine runs 100% better and the total loss of electronic timing advance has not come back. I'm thinking it was the throttle position sensor.
 
It's back! Just limped it home from work. Suddenly crapped out half way home while I was in the fast lane doing 80. It wasn't easy getting to the shoulder in heavy traffic. Did about 8 miles on the shoulder at 15-20 mph! Idles fine, as soon as I try to accelerate, it starts cutting out and popping through the exhaust. Sounds like gunfire! I think I've replaced everything but the ECM and distributor. I got a good week out of it. Time to park it and fire up the old cummins, again!
 
You really should replace the distributer pickup coil. Sounds a lot like its overheating after operating for a bit and then failing.
 
I just ordered a DUI-12620BK from Summit. Hopefully it'll work.
 
Sounds like a pickup coil to me. If you have an oscilloscope it's an easy check.
 
You must log in or register to reply here.

Latest Posts

Top Bottom