87 running lean?

[jesdude7789]

My truck has lost power somewhere and its been a while since i tried to find out whats wrong. It doesnt have any check engine codes but lacks acceleration and responsiveness to the gas pedal. When I push on the pedal at any speed it sounds like the engine revs a little higher than its supposed to and especially if i let off the pedal after cruising at say 20 or 30 mph you can tell that it drops off too many RPMS. I would think its from a vacuum leak somewhere but i've already replaced the intake gaskets a year ago. i rechecked them about a month ago and still good. I also checked the little vacuum lines to the the TBI on both of their ends and they seem fine also. The MAP, IAC, and TPS are all less than a year old and check out fine also. I have been able to watch my live data via my laptop and interface cable. The single wire o2 stays lean at idle and then starts cycling once i rev it a little. then leans again. I don't think it cycles as fast or high and low as it should though. Seems to stay in the middle voltages like .3 to .7 not down to .1 and up to .8 or .9 like i've been told it should. The exhaust sounds kinda cruddy on acceleration which is how i KNOW something has to be wrong. I've had the catalytic converter checked, its good. No holes or anything in the exhaust. The engine has 67,000 original miles on it and has good compression across the board. Could the torque converter not be transferring as much power to the transmission or something like that? Could the AIR PUMP hoses and check valves be contributing? Bad injectors? the fuel pressure is 13 psi. Oh and the entire ignition system is recently replaced as well including the whole distributor. the EGR too. It is really bothering me when it looks like a good truck but it doesnt FEEL like one like it did three years ago. What the heck am I missing?

[menace121978]

not too sure what to tell you besides do the cheap basics 1st. replace fuel filter, check for vaccum leaks w/ a can of carb. cleaner while its running, and check your work on the ignition...such as check plug wires at night with a bottle of windex while its running spray heavy down by the boots and look for pretty arc's.

[jesdude7789]

thanks menace!
I havent tried the windex thing but i'll check the vacuum again as well tonight.
I hope i find something i missed before so it'll be done and run great again! It's the kind of thing that makes it not fun to drive.... which i will not stand for.

[dan76]

Pull a plug or two from each bank and read the electrode.

[rfmaster]

7789

What you are describing is a classic low fuel pressure symptoms. After 20+ years of service either fuel pump or the hose that connects pump to to the tank feed through are getting tired. TBI system is designed to operate at about 13 PSI, but will still function down to about 4-6 PSI. In other words.

Check your fuel pressure at TB
Check fuel filter

//RF

[jesdude7789]

Originally Posted by rfmaster

7789

What you are describing is a classic low fuel pressure symptoms. After 20+ years of service either fuel pump or the hose that connects pump to to the tank feed through are getting tired. TBI system is designed to operate at about 13 PSI, but will still function down to about 4-6 PSI. In other words.

Check your fuel pressure at TB
Check fuel filter

//RF

I replaced both pumps in my dual tank setup about 18 months ago and more recently replaced the fuel filter and put a stainless braided line with Earls anodized fittings from the filter to the throttle body and an inline fuel pressure gauge which reads 13 psi. I also installed CFM technologies adjustable fuel pressure regulator with a new diaphram at the same time. The switching valve is original and i replaced all the rubber hoses from it to the tanks at the same time i did the pumps. Maybe my gauge is wrong?!.......To more accurately describe the sound the engine makes on acceleration is like pinging or knocking but i know the timing is set dead on zero because i replaced the distributor a couple months ago when the magnets were weak and reset the timing with the connector unplugged and reset base idle. I am able to see my coolant temp as the computer does with my laptop and it is working like it should as are all the other sensors. Maybe the fuel injectors are bad somehow but i doubt it because of the low mileage on the engine and when i look at the spray it seems normal.

[crossy's son]

Go outside and Unhook the Coolant temperature sensor on the front of the engine, It is the one right near the water neck, the one that the computer uses.

When you unhook it, it should idle high and run better if thats the problem.

If that sensor is unhooked it is tellling the computer that is -40~F and run full rich.

Try that and see if it helps. Probably won't though

rfmaster is probaly right though, If it is the original pump its probably tired and you MAY have a ripped Fuel Pressure regualtor diaghram. If so it will cause poor fuel pressure and it will stumble.

Does your truck happen to have dual tanks? There may be a restriction in your fuel tank switchover, They were not suitable on a TBI truck from the factory due to the fact there so much more high pressure fuel systems, They simply took all the -86 Dual tank crap and mounted it on a 87 truck and the whole setup was very restrictive, expecially the return lines.

If that valve is not opening all the way you would have fuel problems as well. Thats only if it has dual tanks.

you'll get it figured out man. TBI's are easier than a quadrajet.

Brandon

[menace121978]

sounds like cheap gas and/or the timings off. try bumping up the timing a bit... and like dan76 said check the plugs and see how they read.

[jesdude7789]

Originally Posted by menace121978

sounds like cheap gas and/or the timings off. try bumping up the timing a bit... and like dan76 said check the plugs and see how they read.

I always buy good gas at shell or chevron, never go to walmart or raceway unless i have no choice and even then only put in 5 bucks til i get to a better station. I did try messing with the timing before but i will try some more tomorrow as well as check the plugs beforehand.
thanks

[rfmaster]

OK on fuel pressure - it may be worth checking with another gauge just be sure. The pinging that you are describing maybe due to re-formulated gas (E10). E10 has stoich mixture at 14.3 vs. 14.7 for normal gasoline formulation. It does not take that much but a persistent lean condition with E10 is a common problem for early EFI systems. Knock sensor is working over time in your case taking out timing when you really needed. Hence, sluggish throttle response.

Which software are you running WinALDL, Tuner-PRO?? Can you capture data logs? I wonder what your cross counts look like and BLM's - my guess they are all well above 128-132 region.

//RF

[jesdude7789]

Originally Posted by rfmaster

OK on fuel pressure - it may be worth checking with another gauge just be sure. The pinging that you are describing maybe due to re-formulated gas (E10). E10 has stoich mixture at 14.3 vs. 14.7 for normal gasoline formulation. It does not take that much but a persistent lean condition with E10 is a common problem for early EFI systems. Knock sensor is working over time in your case taking out timing when you really needed. Hence, sluggish throttle response.

Which software are you running WinALDL, Tuner-PRO?? Can you capture data logs? I wonder what your cross counts look like and BLM's - my guess they are all well above 128-132 region.

//RF

I'll order a more professional one, it is a Mr. Gasket gauge i believe and i just got it at the time cuz it was there at oreillys. I would definitely agree that it seems like it does not advance the timing properly ( oh yeah the reman distributor has a new module on it too). I've just been using Tuner Pro so far but not really familiar with it yet, just happy i could see my basic live data so far. Cross counts would go up so far and then start over and my BLM's I will have to check it tomorrow. If you know how to use the program and can tell me what to do to record or anything else useful i would appreciate it!

[rfmaster]

I have used WinALDL extensively in the past - it is some what primitive, but it does the job. I use Tuner PRO -RT for bin file editing (aka tuning) I have not used it for data capture since I have modified my ECM with EBL conversion. EBL - that's another discussion all together.

In your case capture the standard data stream which should contain the following critical sensor data:

SENSOR:IAC
SENSOR:Coolant Temp
SENSOR:SPEED
SENSOR:MAP
SENSOR:RPM
SENSOR:TPS
SENSOR:INT
SENSOR:O2
SENSOR:Battery Voltage
SENSOR:Knock counter
SENSOR:BLM
SENSOR:rich / lean counter

You'll have to define data log file see below:



Define file for capture (Select Log File For Rec/Play)

[jesdude7789]

ya thats how i've had it setup so far and just to look at the live data. Are you saying i should drive it around and record the data? or can i do it at idle and get enough info to determine whats wrong or being affected?

[jesdude7789]

Originally Posted by rfmaster

I have used WinALDL extensively in the past - it is some what primitive, but it does the job. I use Tuner PRO -RT for bin file editing (aka tuning) I have not used it for data capture since I have modified my ECM with EBL conversion. EBL - that's another discussion all together.

In your case capture the standard data stream which should contain the following critical sensor data:

SENSOR:IAC
SENSOR:Coolant Temp
SENSOR:SPEED
SENSOR:MAP
SENSOR:RPM
SENSOR:TPS
SENSOR:INT
SENSOR:O2
SENSOR:Battery Voltage
SENSOR:Knock counter
SENSOR:BLM
SENSOR:rich / lean counter

well i'm not using tuner pro now because apparently the RAW data for the coolant temp is not translated properly in the program. I downloaded WinALDL and it shows everything properly so that means the coolant sensor is not the problem but i have a new one now. haha!

I tried to data log with Winaldl but it doesnt seem to create a file or whatever so i cant look at my driving data. But i will say that my knock counter would go up a couple points any time i put my foot in the throttle so i do have a knocking problem and it is definitely going to retard the timing automatically. now the question is why is it knocking when my timing is set properly, my spark wires are good, and all my sensors seem to be operating properly?

oh ya the screen shot doesnt show it because i reset the program accidently but my knock counter was up to 19 or 20 on a two mile trip during which i accelerated a little more than normal a few times.

[rfmaster]

Ideally, Yes (you may need to get sig lighter to lapy DC-DC converter)

Do you you feel that you lost power at certain range of RPM's while you driving? Then you'll have to capture that engine performance data and the same operating conditions.

Another thought - double check your spark plug routing and re-verify that spark wires are in good shape. One more than occasion I had engine hesitation that was eventually traced down to old spark wires arcing over. Just a thought (and does not cost anything). With engine running, in a dark garage, spray spark wires with a fine water mist. If you see blueish halo around wires or see engine stumble - you found that rascal.

//RF

[jesdude7789]

Originally Posted by rfmaster

Ideally, Yes (you may need to get sig lighter to lapy DC-DC converter)

Do you you feel that you lost power at certain range of RPM's while you driving? Then you'll have to capture that engine performance data and the same operating conditions.

Another thought - double check your spark plug routing and re-verify that spark wires are in good shape. One more than occasion I had engine hesitation that was eventually traced down to old spark wires arcing over. Just a thought (and does not cost anything). With engine running, in a dark garage, spray spark wires with a fine water mist. If you see blueish halo around wires or see engine stumble - you found that rascal.

//RF

I feel it lost power across the entire range, but it is more noticeable at neighborhood and town cruising. On the highway tho i have to constantly check my speed and usually put my foot in it to keep up at 70 or so. It doesnt make the power to keep itself up there as easily as it used to.

I am going to hook up to my laptop in a bit and check my live data and write it all down as it is set at idling conditions when hot and then i will post and see what ya'll think. oh ya and i will say that when i made a hard stop the other day at a light the engine stumbled and died and then started back up. And it is hard to start cold (four to six seconds)but usually easy when hot already(one or two seconds).

I did the water mist on the spark plugs and wires though and did not see anything and the routing is correct. The cap, rotor, plugs and wires are all about two years old. ACCEL parts except for the wires, they are oreilly house brand

[jesdude7789]

Wow I think i just found the problem guys. I used my tuner pro and drove the truck around town a few miles til it was hot and everything, came back to the driveway and hooked up the laptop and the pics will show you my values at idle and then again at about 1000 rpm holding it steady. It looks like the coolant sensor is the culprit. 44 degrees celcius is only 110 farhenheit which is not what my temp gauge reads. it shows 180. I am on my way to getting a new sensor and hope it works!

[crossy's son]

Make sure you unhook the brown wire under the brake booster to advance the timing.

That really makes a difference on TBI trucks, advancing it 3* on my dad's 87 305 made a big difference in throttle response/power.

[glock35ipsc]

Originally Posted by crossy's son

Make sure you unhook the brown wire under the brake booster to advance the timing.

I did this recently to my converted 85. Only when I unplugged the brown wire, the truck died instantly. Any thoughts on that?

rfmaster - Would you mind taking a look at my thread when you have time? I'm having a surging issue at cruise. Thanks!

http://67-72chevytrucks.com/vboard/s...d.php?t=351755

[menace121978]

right on man! hope it works out!!!

[jesdude7789]

well bad news....i replaced the coolant sensor and cleared the computer memory by disconnecting the battery for ten minutes. I just drove it home about 15 miles coming from a friends house. It seemed to accelerate better but i think that is because i reset the memory because when i got to the driveway and hooked up my laptop again to read the live data it still shows 47-48 degrees celcius! when i tested the resistance across the pins on the sensor it said 198 ohms which should translate to 190 degrees farhenheit or about 90 degrees celcius! Could the translating software be wrong on tuner pro or is there some weird wiring problem on my truck? Or is the ECM not translating the voltage properly? Plus the engine still sounds funny on acceleration like the wrong fuel ratio or timing not being advanced properly. Damn.