seraphiem
New Member
First off, I would like to thank all who contribute, both the regulars and irregulars. As with most cult car forums (unlike the boy racer stuff), this one has provided an exceptional amount of technical information while still being very civil and mature.
I bought a ’93 ATX with 140k miles about three weeks ago as my second or project car and have been quite happy with it. When I picked it up it ran great and was super clean minus a noisy suspension in need of work. Over the course of the 2500 some odd miles I have driven it I have watched my fuel consumption go from about 18 mpg down to anywhere from 9 – 12 mpg currently. Note, this is extreme stop and go driving. Traffic by me is beyond comprehension. I don’t consider myself ‘beating’ on it, but do like to wind it out every once in a while when I get the chance.
Over the course of the past three weekends I’ve done rather simple preventive maintance. First thing I did was change the oil and filter, along with a new T-Stat and flushed the coolant system. Before hand I was getting wild temp fluctuations for the coolant and this brought it down to a constant ‘L’ reading.
After pulling the codes I got the common 332 and 176 codes (along with the IMRC 551) I set about vanquishing that ever bright and annoying CEL. Well after replacing the air filter and cleaning the front plug wells, I pulled the TB off to clean the nostrils. The EGR nostrils were no doubt severely coked up but the top IAB nostrils were rather clean and obstruction free. Buttoned everything back up and the car seems good to go. Drove it for about 200 miles and all seemed well until the CEL (172 and 551 this time) sprang back up, and now, the idle oscillates when in park or neutral. IE, the idle speed shoots up to 1100 and then down to 500-400, up to 1200 and then stalls. The strange thing is, it will not do this when first started up or after I start it back up after a stall. Only after coming down from speed.
Frustrated, I cleaned the MAF filaments along with the IAC/IAB. Both units did look brand new and the PO did say he replaced a few sensors. Reset the Idle speed program and applied loads as appropriate while the computer is learning. Same result, horrible oscillatory idle until the engine eventually stalls.
While trying to hunt down vacuum leaks I finally figured out the secondaries were not closing on start-up. That 551 made sense as I finally found the unplugged plug for the IMRC solenoid. Wow, the car runs like a bat out of **** now. But, found no vacuum leaks and the car still stalls.
That’s at the point I’m currently at, I’m hoping a working IMRC would bring my mileage upto a more tolerable level but I have my doubts.
So does anything sound glaring? I haven’t tested/replaced the TPS but I have doubts that it would affect my idle (or fuel consumption) this much. The same thing with the O2 sensors, my understanding is that bad O2 sensors would cause bad mileage but have minimal impact on idle speed. They also look rather new. The plugs and wires look newer, (non-Motorcraft) but who knows how they are. No tell-tale signs of misfire though. KOER tests proved no codes at all and cylinder balance test came back good.
My only guesses left are the TPS, ECT, and possibly plugged/bad cats. The car does perform well when moving so I have doubts about the exhaust being plugged. And I have a constant ‘L’ reading from the ECT which seems consistent with other forum members.
So again, anything that I haven’t thought about or covered? The idle doesn’t bother me too much, its getting the 9 – 12 mpg and thinking about my cats burning themselves up and spitting back up the EGR that gets to me.
I apologize for such a long-winded thread. I just always like to put everything up front.
I bought a ’93 ATX with 140k miles about three weeks ago as my second or project car and have been quite happy with it. When I picked it up it ran great and was super clean minus a noisy suspension in need of work. Over the course of the 2500 some odd miles I have driven it I have watched my fuel consumption go from about 18 mpg down to anywhere from 9 – 12 mpg currently. Note, this is extreme stop and go driving. Traffic by me is beyond comprehension. I don’t consider myself ‘beating’ on it, but do like to wind it out every once in a while when I get the chance.
Over the course of the past three weekends I’ve done rather simple preventive maintance. First thing I did was change the oil and filter, along with a new T-Stat and flushed the coolant system. Before hand I was getting wild temp fluctuations for the coolant and this brought it down to a constant ‘L’ reading.
After pulling the codes I got the common 332 and 176 codes (along with the IMRC 551) I set about vanquishing that ever bright and annoying CEL. Well after replacing the air filter and cleaning the front plug wells, I pulled the TB off to clean the nostrils. The EGR nostrils were no doubt severely coked up but the top IAB nostrils were rather clean and obstruction free. Buttoned everything back up and the car seems good to go. Drove it for about 200 miles and all seemed well until the CEL (172 and 551 this time) sprang back up, and now, the idle oscillates when in park or neutral. IE, the idle speed shoots up to 1100 and then down to 500-400, up to 1200 and then stalls. The strange thing is, it will not do this when first started up or after I start it back up after a stall. Only after coming down from speed.
Frustrated, I cleaned the MAF filaments along with the IAC/IAB. Both units did look brand new and the PO did say he replaced a few sensors. Reset the Idle speed program and applied loads as appropriate while the computer is learning. Same result, horrible oscillatory idle until the engine eventually stalls.
While trying to hunt down vacuum leaks I finally figured out the secondaries were not closing on start-up. That 551 made sense as I finally found the unplugged plug for the IMRC solenoid. Wow, the car runs like a bat out of **** now. But, found no vacuum leaks and the car still stalls.
That’s at the point I’m currently at, I’m hoping a working IMRC would bring my mileage upto a more tolerable level but I have my doubts.
So does anything sound glaring? I haven’t tested/replaced the TPS but I have doubts that it would affect my idle (or fuel consumption) this much. The same thing with the O2 sensors, my understanding is that bad O2 sensors would cause bad mileage but have minimal impact on idle speed. They also look rather new. The plugs and wires look newer, (non-Motorcraft) but who knows how they are. No tell-tale signs of misfire though. KOER tests proved no codes at all and cylinder balance test came back good.
My only guesses left are the TPS, ECT, and possibly plugged/bad cats. The car does perform well when moving so I have doubts about the exhaust being plugged. And I have a constant ‘L’ reading from the ECT which seems consistent with other forum members.
So again, anything that I haven’t thought about or covered? The idle doesn’t bother me too much, its getting the 9 – 12 mpg and thinking about my cats burning themselves up and spitting back up the EGR that gets to me.
I apologize for such a long-winded thread. I just always like to put everything up front.
