93 Astro Idles and runs erratically

Quarter Million + · 02-02-2009, 03:09 PM

4.3 Engine code Z throttle body injection. Was driving on the expressway and lost power and the engine has run irregular since. Pulled code 44; Lean fuel @ o2 sensor. Replaced fuel pump, fuel filter, injectors throttle body, idle air control, throttle position sensor, map sensor, and fuel pressure regulator. No effect (Except boosting sales in the local economy). It runs rough and stalls at idol. Lacks power. I need it for work, so I unhooked the map sensor's vacuum to default the computer and make it run in limp mode to get around. I plugged the map vacuum line and can force it to get me around but remain clueless as to the problem. (the dist cap, rotor, plugs, and wires are fairly new and show no signs of trouble, like cracks, cuts, etc.)

brcidd · 02-02-2009, 03:50 PM

Except for the code, it sounds like a stuck open EGR valve pintle-- have you cleaned it out? Should have set a code 32 though...at some point...

Quarter Million + · 02-05-2009, 08:48 PM

Thanks brcidd, It never threw a 32. Disconnecting the MAP set 33,34,and 35. I sucked on the vacuun line to the EGR and felt the diaphran move with my hand but it did not dawn on me to remove it and check the pintel. When I replaced the throttlebody I saw a minor collection of burnt oil down in a champer where the intake port for the PCV valve is, but I had blown through the vacuum line before I changed it remembering how the 350's with the quadrajets get fouled up there. The van has 266200 miles on it. It goes 65 on the highway but loses momentum on hills. (Fortunately I live in Florida and it's mostly flat except for overpasses). It also won't climb past 40 going over causeways. That's still with the MAP disconnected. Also stalls at stops. It's alot like driving a stick now. I'll check it Saturday 2-7 if the weather is above 40 degrees in the morning. Gotta work in the mean time.

discnik · 02-06-2009, 01:09 AM

Does the vehicle have an Air Injection Pump ? Is so you may want to check the valve for proper operation.

Quarter Million + · 02-08-2009, 10:46 PM

No air injection pump. I checked the EGR valve today and it's functioning and seats well. I cleared the codes and ran it again until it threw one. Again Code 44. I unplugged the O2 sensor and it had no effect. The Chilton's says it's the O2 or maybe and open wire to the ECM. Following the path of bad EGR, I checked for leaks in the intake gasket, first visually, then with spray. Gasket is fine. Throttle body gasket is new. Also the one on top and bottom of the riser over the throttle body to the air cleaner housing are new. I started it as soon as the EGR was checked, with the riser off (just to see if it ran smooth before re-assembly, which it did NOT) and heard alot of air rushing through the port where the idle air adjuster is and chose to plug it with a thick baggy to see the effect (and verify it works). Regulating the amount of airflow through that potion of the intake had no effect either which leads me to question the HEI? I don't know what the term for the Hall Effect switch under the rotor is, but could either of the 2 components that plug in at the base of the distributer cause this issue? It seems mechanical, rather than electrical, OR, the ECM isn't intrepiting the timing signal. It runs, doesn't backfire, but misses irratically like a cracked cap, or intermittant open in the rotor. I took a radio over the distributer to hear if a plug was fouled or missing, but the static on the radio confirmed irratic behavior. If I leave the MAP hooked up, it stalls every time at idle and keeping my foot on the gas pedal to run the engine as slow as possible and not stall, it fires the cylinders erratically (unevenly) and wont maintain an even RPM at any slow speed to take a timing reading to see if the chain is real loose. Without the MAP it idles after a couple of blips on the gas but the rpm's vary. I even put the old MAP sensor back in to see...no effect. No difference between how the engine runs between the 2. ECM's next if I can't get a solution here. Oh and as the manual suggested, I checked the VISIBLE wireing for nicks, cuts or opens and found NO damage to the insulation or plug ends. I broke the lock on the TPS but it plugs in sloid with no obstructions.

Quarter Million + · 02-18-2009, 04:25 PM

Ok, now I've replaced the whole distributer, including plugs, wires, cap, and rotor. Checked coil ohm readings and replaced the ECM computer under the passenger side kickplate, so I still think it's mechanical because I've changed ALL the electrical and the issue persists....it feels as if it's leaking air (vacuum). The diverter for the AC actuated well after the van had stopped, so the cruise and plenems hold air, Is there a chance the intake manifold could get a hole from its underside or the gasket fail (The engine has never overheated and was running fine until this problem happened suddenly while driving 65 down the expressway). Could the timing chain jump a tooth (I don't drive the van hard). Still clueless, broke now too. Still sputters and won't idle with the MAP hooked up but will go (very sluggishly) with the air line to the MAP disconnected and Plugged at the throttle body. Hints please!

Quarter Million + · 02-25-2009, 10:31 PM

Coming off the expressway today, I noticed a cadilitiac converter smell. Could this be causing this problem? (Partial plug / meltdown) still stumped and not repaired. It takes almost 1/2 a mile to get to 65, luckily I go far to work. Hints please!

CD Smalley · 02-28-2009, 08:19 AM

Those VIN Z engine are known for gasket failures between the TBI unit and the intake. To test.
Take a can of carb spray and spray around the base of the TBI. If the engine smooths out. You've found it.

Quarter Million + · 03-04-2009, 10:58 PM

Thanks CD Smally, did that on 2-8, Put a new gasket under the new intake. Torqued to 40. No effect. Yesterday, 3-3, I was coming off the expressway and popped it into neutral so I wouldn't stall at the light, gave the gas a blipp and the van shuttered, ground for a second and died. I tried to restart it but had no starter engagement. Looked at the pointer and I had accidently overshot neutral for reverse! The pop was the front drum breaking the weld. Now I have park, neutral, first, and third. Reverse, second annd forth are waiting for my shipment from DACCO with a new drum and related gaskets. I'm going to check top dead center tomorrow with a coat hanger in the bore and a socket on the crank to see where the pointer rut is on the flywheel when the piston tops to check the timing chain, the intake may come off next. I can't afford a replacement vehicle, work is drying up fast, but I won't fix the transmission until the engine returns to running normal, but at least I know what to fix on the trans. 269086 miles now. Still guessing...

Quarter Million + · 03-13-2009, 11:01 AM

With the van stalling at almost every stop and no funds to put it in the shop, I put to RIP at the scrap metal salvage yard. Never found the problem. Good luck with yours.

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