car is running lean...

[joel5.0]

Nothing, and it has nothing to do with the readings at the MAP sensor.

The Speed Density fuel injection system is based on an assumption of the volumetric efficiency of the engine. When you modify the engine from stock, you're changing it's volumetic efficiency, however the computer cannot compensate for this because it has no way to know.

So as you do mods like a free flowing exhaust, that ultimately allow the engine to breath more air, you're not getting any more fuel with it, and you go lean. Even with all the electronics working.

Fordguy,

Your sig says that your 87 is mostly stock. If that's true, you shouldn't have any mod-induced lean condition. The fuel pressure numbers you're getting are what they should be.

Take it from someone who worked in a shop, you don't want to take your car to one. Shops throw money and parts at cars, they catch hell trying to charge customers diagnostic labor hours to actually troubleshoot a problem so they don't even try. A bad temp sensor could be the cause, but I seriously doubt that was more than an educated guess. If you want to know what's really wrong and not pay out the nose for it, you're going to need to do the troubleshooting yourself.

Pull codes like JR suggested. Off the top of my head, test your coolant temp sensor (new doesn't mean good), your intake air temp sensor, your MAP sensor, and your EGR position sensor... a remote possibility is there's something up with the EGR position sensor, telling the computer the EGR valve is open when it's not. When the computer thinks the EGR valve is open it pulls out fuel.

If the system goes lean, lean code failures should be output by the system informing any fuel trim correction required falls above the EEC fuel trim capabilities. If this would not be true, installing 24# injectors in a SD system wouldn't be a problem, yet, it is....... with the 42 and 92 system rich codes showing in a self test...... have I done it?..... yep, found out about it back in 1992.

The generalization that SD systems do not monitor A/F and not try to correct any deviations from the optimum stoichiometry is wrong, otherwise, they would not have passed EPA regulations. SD systems "fault" is that they attempt to correct A/F "after the fact", based on engine vacuum output as a signal of their efficiency however, the O2 inputs are also used (provided closed loop is achieved)..... IOW, the EEC does have a way to know. Have I worked street SD setups with 80mm TB's, better flowing intakes, exhaust systems, cat-less non-emissions, better flowing headers (ST's and LT's)?......... yep.

 

[seijirou]

If the system goes lean, lean code failures should be output by the system informing any fuel trim correction required falls above the EEC fuel trim capabilities.

Right

If this would not be true, installing 24# injectors in a SD system wouldn't be a problem

I don't understand what you're trying to get at here. If the system doesn't output lean code failures when the system goes lean then installing 24# injectors wouldn't be a problem?

, yet, it is....... with the 42 and 92 system rich codes showing in a self test...... have I done it?..... yep, found out about it back in 1992.

Of course, SD, MAF, or otherwise, almost every fuel injection method out there assumes a certain injector volume rate. You can't just change the injector volume without telling the computer and expect it to work. This isn't SD specific.

The generalization that SD systems do not monitor A/F and not try to correct any deviations from the optimum stoichiometry is wrong, otherwise, they would not have passed EPA regulations. SD systems "fault" is that they attempt to correct A/F "after the fact", based on engine vacuum output as a signal of their efficiency however, the O2 inputs are also used (provided closed loop is achieved)..... IOW, the EEC does have a way to know. Have I worked street SD setups with 80mm TB's, better flowing intakes, exhaust systems, cat-less non-emissions, better flowing headers (ST's and LT's)?......... yep.

I'm not saying that SD systems do not monitor A/F and cannot make adjustments. I'm saying that SD systems pivot on an assumed volumetric efficiency, for which it cannot detect deviation. You can alter volumetic efficiency simply by increasing or decreasing ring seal.

the SD system can add or pull fuel, but only after it's gone lean or gone rich. It still reacts to your foot by it's programming, it then reacts to that instinct-response based on what the O2 sensor report. However, if you're foot is constantly fiddling with the throttle, changing throttle position and engine load, the computer is going to just as constantly give you it's programmed response. The SD computer can't really get the A/F back to stoich until you're cruising.

Cruising emissions by the way, are what the EPA cares about.

 

[joel5.0]

Right
the SD system can add or pull fuel, but only after it's gone lean or gone rich. It still reacts to your foot by it's programming, it then reacts to that instinct-response based on what the O2 sensor report. However, if you're foot is constantly fiddling with the throttle, changing throttle position and engine load, the computer is going to just as constantly give you it's programmed response. The SD computer can't really get the A/F back to stoich until you're cruising.

Cruising emissions by the way, are what the EPA cares about.

That is exactly how the system works as soon as the O2's reach close loop status, but not limited to cruising conditions only. Keep in mind that wide bands are not used, stoich status is defined in terms of a HEGO "rich-lean" switch or "jumpback" function, not a specific output signal from the O2's. IOW.... the system is going lean or rich constantly therefore, applying fuel trim under ALL driving conditions.

The point I'm trying to make is simple, the fact that a camshaft upgrade is something that will affect the SD system capabilities when compared to a MAF system, does not mean the SD system is less capable to deal with A/F control under changing circumstances or other upgrades. Based on your statement, close loop control is only limited to cruising conditions in a SD system, and that's not the case. View attachment 307954 ... if cruising emissions is what the EPA cares about, why have I been working cases that fail emissions testing at idle for the past 16 years? .... or, why would they establish emissions requirements for driving conditions other than cruising?

 

[seijirou]

That is exactly how the system works as soon as the O2's reach close loop status, but not limited to cruising conditions only. Keep in mind that wide bands are not used, stoich status is defined in terms of a HEGO "rich-lean" switch or "jumpback" function, not a specific output signal from the O2's. IOW.... the system is going lean or rich constantly therefore, applying fuel trim under ALL driving conditions.

Well you automatically go in to open loop beyond a certain throttle position. If you're doing any real accelerating you're not in closed loop. So again, the computer is responding based on it's programming. It's not doing any fuel trim. I guess using the word cruising was a bad choice. Maybe it makes more sense to use a phrase, "cruising around". That could be steady speed, light acceleration. Grandma driving basically.

The point I'm trying to make is simple, the fact that a camshaft upgrade is something that will affect the SD system capabilities when compared to a MAF system, does not mean the SD system is less capable to deal with A/F control under changing circumstances or other upgrades. Based on your statement, close loop control is only limited to cruising conditions in a SD system, and that's not the case.

I guess we just fundamentally disagree here. I don't think it's true that the SD system is just as capable of dealing with A/F under changing circumstances and/or upgrades. Again, you're not in closed loop under any real acceleration. So under any real acceleration, the SD computer still plays like you have a stock engine. You can get away with some mods because the factory tune under open loop is on the rich side. Not because the SD computer is actually adding fuel due to mods. Keep doing mods and eventually you're going to exceed that margin and go lean.

View attachment 307934 ... if cruising emissions is what the EPA cares about, why have I been working cases that fail emissions testing at idle for the past 16 years? .... or, why would they establish emissions requirements for driving conditions other than cruising?

Idle, in my mind, is still a "cruising" situation. If you've know the EPA to care as much about WOT situations as they do about light or no-throttle situations, than I don't have an answer. Your experience is different than mine.

 

[joel5.0]

Well you automatically go in to open loop beyond a certain throttle position. If you're doing any real accelerating you're not in closed loop. So again, the computer is responding based on it's programming. It's not doing any fuel trim. I guess using the word cruising was a bad choice. Maybe it makes more sense to use a phrase, "cruising around". That could be steady speed, light acceleration. Grandma driving basically.

WOT..... yes, partial throttle...... how, at what point? You're also overlooking the results of the Adaptive Strategy...... present in all '86+ models and the '85 exception with the Tempo/Topaz models with the HSC/CFI engine. The strategy does change the base programming and uses its learning, to update open loop tables and functions. Fuel trim is part of the EEC logic/program in SD systems.

I guess we just fundamentally disagree here. I don't think it's true that the SD system is just as capable of dealing with A/F under changing circumstances and/or upgrades. Again, you're not in closed loop under any real acceleration. So under any real acceleration, the SD computer still plays like you have a stock engine. You can get away with some mods because the factory tune under open loop is on the rich side. Not because the SD computer is actually adding fuel due to mods. Keep doing mods and eventually you're going to exceed that margin and go lean.

Again, at WOT (=2.71 vdc over the minimum closed throttle position)..... yes, but the open loop tables will be the Adaptive Strategy "upgraded" versions, which use what is called a Long Term Fuel Trim (LTFT) "correction" value.

 

[fordguy87]

okay i just tested the voltage at the coolant temp. sensor and that reads fine so thats working. So i start looking at the EGR diaphram on the back of the egr plate and i tried to push in alittle on it and it wont budge. I started the car and then unpluged the connector underneath of it and I expected the engine to bog down or do something but it didn't. I also unhooked the vacuum line and the engine ran the same just as bad not worse not better. Could that maybe be causing my backfiring and sputtering problem?

 

[seijirou]

okay i just tested the voltage at the coolant temp. sensor and that reads fine so thats working. So i start looking at the EGR diaphram on the back of the egr plate and i tried to push in alittle on it and it wont budge. I started the car and then unpluged the connector underneath of it and I expected the engine to bog down or do something but it didn't. I also unhooked the vacuum line and the engine ran the same just as bad not worse not better. Could that maybe be causing my backfiring and sputtering problem?

Those things that you did shouldn't have produced any results when things are working correctly. So that's good that nothing happened.

 

[joel5.0]

Speed density systems may have a faulty MAP sensor (out of calibration range) w/out logging a failure code (code 22). Since backfiring through the intake = fuel starvation..... you may want to check how the engine runs by causing a partial vacuum leak at the MAP sensor hose (force a richer A/F correction)........ if the engine runs better and little or no backfires are noticed, you may want to "borrow" a working or KGU (Known Good Unit) BP/MAP sensor to test it in your car. The other alternative to this one, would require you measure the frequency output (Hz) of the MAP and compare it with the vacuum output from the engine to the table shown below..... LUK

 

[fordguy87]

ok just did a compression check and this is how my test went

Back of engine
105 130
125 120
110 115
105 110
Front of Engine

now I just read you are supposed to have the engine warmed up before doing this but i didn't.

 

[seijirou]

ok just did a compression check and this is how my test went

Back of engine
105 130
125 120
110 115
105 110
Front of Engine

now I just read you are supposed to have the engine warmed up before doing this but i didn't.

Warm it up and do it again

 

[fordguy87]

While doing the test I also found something else. I dont know if its related to why my car is backfiring or not but the hose that goes from the smog pump to the valve where the vacuum line is hooked up was up against the header and melted a hole through.