1988 idles but stalls and backfires

[geardrivensoul]

My dad has an 88 with a frustrating problem. It will start and idle but anywhere past idle it will pop through the intake and backfire and often stall. So far he's done the cap rotor and HEI, it has a brand new battery, fuel filter. We've run a fuel pressure test and it holds 32-34 at idle, off idle the guage bounces wildly from 0 to about 48. Also the entire exhaust gets extremely hot from front to back. It is not throwing any codes. Engine basic 101 says this a too lean condition, but any advice is appreciated......maybe we'll get it fixed just in time to park it for the winter.

[c4c5specialist]

HI there,

Please check the resistance on the injectors first.

16.5 ohms is what is necessary.

Post your findings.

Allthebest, c4c5

[geardrivensoul]

Ohm test - all 8 are 16.2 or 16.3. My dad has ordered a fuel pressure regulator. Is that a possibility?

[ChuckG]

Did you test your fuel pressure?

I'd also look for clogged cats....

[geardrivensoul]

Fuel pressure is 32-34 at idle. Once off idle while its stumbling and backfiring it bounces around (a lot). Whats the best test for clogged converters? The entire exhaust clear to the to the middle of Y pipe in back gets extremely hot.

[ChuckG]

Don't know of a 'test" per say, but limited exhaust pressure out of the pipes would cause me to pull the cats and check visually.

Fuel pressure should be closer to 40PSI. Have you changed the in-tank pump?

[LLC5]

Originally Posted by geardrivensoul

Fuel pressure is 32-34 at idle. Once off idle while its stumbling and backfiring it bounces around (a lot). Whats the best test for clogged converters? The entire exhaust clear to the to the middle of Y pipe in back gets extremely hot.

You can use a vacuum gauge to check for a restricted exhuast system. Install the vacuum gauge to an intake manifold port, and when the engine is warm accelerate to full throttle (in neutral or park is fine) while watching the gauge and it should drop to near 0 on WOT with a unrestricted exhaust system. This won't tell you exactly what/where the restriction is, but it can tell you if there is one. Good luck with it.

[geardrivensoul]

The fuel pressure regulator did not fix, we will try to test the exhaust part before moving on to the pump. Thanks all!

Update: the engine vacuum showed 18-20 at idle, so we moved to replace the fuel pump, and I'm happy to report that fixed it. It is now for sale, time to upgrade....thanks again for all that responded to help out.