My 91 z has a 305tpi in it and im trying to make it work before i put my 350 in it in the next couple months. Well i just finally changed my injectors to the 19lb bosch ones that i have had lying around and my car is still running like crap and the pressure still drops at the same rate.. Wont idle right when it gets hot likes to surge And then it will surge so drastically it kills its self? the exhasut also burns my eyes. Trying to fix problem so i dont have same problem when i transfer all the parts over. Any ideas,The car has an adjustable regulator as well

I turn key jumps up to 46 psi with vac installed with in 30secs its at 30 psi. 1 min its at 20psi
I start car vac installed car pulsates beween 37-38 vac off it jumps to 47 and it stays.
turn car off with vac installed falls the same rate as with key on

from what i have read it could be a regulator or pump? thanks guys

 

anyone?

 

I think that what you are seeing with the fuel pressure is normal.

Part of your idle problem is that the fuel pressure is probably too high for a stock 305. Lower the fuel pressure to 44psi with the vac line off, motor running, and see how it runs.

Also 19lb fuel injectors are going to be too small for a 350, you'll need 22lb at least for that engine.

 

the diaphrams in the pressure regulator fails some time in aftermaket upgrades. check the tps value and coolant sensor value connections. Id imagine either the fuel is leaking through the diaphram OR the pulsator on the fuel pump is leaking in tank.. Check valve on FP are prone to failing when dealing with autozone fuel pumps.

 

by 3- 5 mins the fuel pressure is at 0 when i turn car off and also when the key is in on postion. I was just hoping that would explain why my car bucks/surges while driving when its warmed up, and why i cant keep a steady idle

 

if you are handy... check and perhaps replace the pick up coil if you've never done it...


edit: ... this is if the problem persist after you've fixed your drop in fuel pressure... ...

 

how do you check this ?

 

lol how do you check this too

 

To check tps turn key to on position engine off (not start) and probe the top two wires of the TPS by the Throttle body. should be .54volts if it negative, change the probe polarity. Unsteady tps will jump erratic while opening the throttle plates by pulling back the throttle body lever, sweeping slowing up and down and check for crazy readings-- it should steadily increase voltage. TO Check the coolant sensor, probe the wires of the coolant sensor and should read 5 volts cold engine with key to on position, and when started it will gradually decrease from 5 to less than 1 volt. If it stays at 4-5volts until fully warm, its bad, or if you test the resistance of the CS* and if it have continuity - its bad. Check for broken wires also leading to the sensor. Heres an interesting link i recommend* ( http://www.aa1car.com/library/coolant_sensors.htm ). And to theres ways to check the fuel pressure reg by smelling the vacuum hose off the FPR* or test with a vacuum tester should hold vacuum. If the check valves on the EVAP system are bad they will release concentrated fumes from the tank-->to purge EVAP canister-->thottle body. for the leak down fuel PSI issue, Yeah theres a pulsator in the tank that slips on the fuel pump, it can leak into tank, the FP is rated like 130psi or so. I have neoprene hose that came with a GM dealer Replacement Fuel Pump(a/c delco), I didn't screw the hose clamp that well and it leaks down from 40ish to zero in less than 20 seconds. BUT it runs great still. IF the fuel pump was replaced recently with an autozone pump, the check valve on the pump will leak pretty fast after two months. To test the check valve, I clamp (hose plier Clamps not visegrips) the return line and check for leak down, if it leaks down after applying 12volts for to the G terminal ,under the dash on the Diagnostic link, then the FPR isnt bad, but the fuel pump or injectors are leaking. But you mentioned new injectors so its not them, Then Maybe the fuel pump check valve or leaking pulsator. But if the pressure holds then the FPR is bad. The ideal pressure is around 42psi for 305. (wanted to add..dont apply the voltage to the G terminal for more than needed to reach 50psi on the Fuel pressure gauge for the test, because the fuel pump can reach over 100psi REALLY FASTand with the return hose not relieving excess pressure, the worst case is it could possibly burst the clamped return hose or possibly damage the injectors, remember stay under 50psi on controlled tests.) Probing the wires isnt ideal way to test, At summitracing they have pigtails that snap in between sensor connection to eliminate the need to probe. But i just probe and make a dedicated probe spot specifically for test readings.

 

tps sensor is fine. checking rest today

 

coolant sensor is fine. The minute the car hits closed loop the idle starts to surge and the exhaust starts to really burn my eyes Checked injectors as well just to see if maybe.. They are all at 17ohms

 

to check the pickup coil, (not ignition coil). Remove the cap and rotor from the distributor, and you'll see the ignition control module. theres a connector with two wire connect to the ignition control Module, the two terminal connection wire should lead to the pickup coil which is under the ignition module. with a volt meter set to resistance, and test,- haynes manual say between 500-1500k ohms is good, any other values indicates bad pickup coil, slightly jiggle the pickup coil leads while testing, wire connections to the on the coil fry sometimes. I had mine coil fried with the broken permenant magnet in 4 pieces. basically tells the computer what cylinder the rotor is at so it can Fire and inject at the right time. WHen mine failed, i couldnt keep idle, i thought it was the ignition coil but it was just bad timing due to whacked values being fed from the pickup coil to the ignition control module and the ecm. might want to check for crossed spark plug wires, i believe its odd numbers on driver side of block and even on passengers starting with front drivers side (front of engine) #1 cylinder.. Also the pickup coil doesnt need to be probe through the wire insulation but rather the slip on terminals can slide off the ignition control module for testing. The ignition control module is delicate and requires thermal grease underneath (if removed, no necessary) on the ground plate attached to the module to prevent overheating of the module and failure.

 

Is this it? if so it read .07 ohms

 

is it the 2 wires underneath the rusty peice the rotor sits on

 

tested fpr and it does not hold a vaccum at all the minute i apply vaccum it starts to fall

 

http://contentinfo.autozone.com/znet...DR132/image/4/ looks like this. wiring diagrams show the pink wire goes to ignition key switch and white to instrument cluster. I cant tell for certain. I've been reminded about the 91' and 85' having different distributors external coil distributor compared to in cap coil hei on the 85'. im not familiar with external ignition coil distributor. but ill find out by tomorrow.

And yeah do you smell gas in the vacuum line of the FPR. the fpr should hold vacuum for sure. if the FPR doesnt hold, that cause a vacuum leak in the vacuum system of the vehicle causing hesitation and idle choppy stall. Cause you got a map sensor* it RELIES on vacuum for fuel curve no vacuum to the map sensor and you dont got power. On my 85' I got a MAF system, relies on air entering the throttle body that cools a hot wire that varies voltage to the ecm. I had to replace the FPR a couple years back, 23 years with a stock FPR is pretty good.

 

nice thank you going to order one tomorrow. I smell fuel when i apply the vaccum.

 

I had the same problem with my 350 tpi. I changed the computer because I could'nt find another culprit. Took the FPR off and sure enough it had a pinhole in it. I replaced it and it solved my problems.

 

When you order, see if you can order just the diaphram from the same company, cheaper, ask their tech if your situation calls for a new diaphram. It would suck if after a complete disassembly hours of work, and it didnt work, id hate to steer you wrong.. but good luck

 

no worries and thank you for all your guidence im gonna pull it apart and check the diaphram to see tomorrow i hate taking off the plenum

 

i replaced the diaphram not sure its right its for a afpr it was a stock replacement but the pressure seems to be ok and it hold ok. I found the vaccum leak tho it wasnt the diaphram at all it was where the vaccum port conects to the regulator. i sealed it up the vaccum holds but it didnt solve my problem. lol it actually made it worse.

 

exhuast burns my eyes even worse and car shuts off faster with out surging as much and my vaccum is at around 20 while running and it bleeds of pretty fast.

 

so then that only leaves your injectors as the likely problem? You know what check for voltage at the injector plug after you've turned off the ignition..

 

the injectors are rebuilt and flow tested how can you tell if they are bad if they ohm out with in .5 of each other

 

did you check your evap check valves with vacuum gauge. what color is the exhaust black? Is she throwing any codes?

 

i read this thread where this guy forked out hundreds of dollars to diagnose, even by 80's mechanics couldnt figure it out, makes no difference. But in the end his fuel pump was shot. He had crossfire injection through. but when my pump failed it sucked.

 

no codes exhasut is light grey/white i guess and when its warm there is no color. And no codes i wish would make it easier.

 

That is not a picture of the pick up coil in the small body HEI dist. Close but not quite. And the pink and white wires are on the ignition coil, not the pick up coil. .7 ohms is just right for the ignition coil primary. The pick up coil has one green, one white wire and connects to the back side of the ign. module. Replacement requires disassembly of the distributor and its no picnic. The relationship between closed loop and your problem doesnt sound like a pick up coil but more like a closed loop fuel control issue. A pick up coil would cause it to not start at all or be more intermittent. However you should test it to be sure. As far as fuel pressure goes, if your FPR diaphram were ruptured you would see fuel coming from the vacuum port with the hose off and engine running. The drop in fuel pressure with the engine off is normal. When you turn on the key, the ECM turns on the FP relay for 2 seconds then shuts it down and waits to see a signal from the pick up coil showing that the engine is cranking before it turns it back on. The system may only hold pressure for 20 seconds. Thats okay. I would start diagnosis with a scan tool. Watch the 02 sensor voltage as the car goes into closed loop. Does the system go into closed loop? Most single wire 02 systems wont go closed loop at idle. The ECM goes closed loop when it sees the 02 change at a given rate. Single wire 02s often dont heat enough from exhaust flow at idle and require increased rpm to reach temp. 02 sensors dont work properly below 600f. Start the engine and allow it to warm up. As the poor idle starts, check fuel pressure, should be about 35 at idle with vacuum connected. Watch 02 as you open the throttle to attain 2,500 rpm. This is the speed for testing 02 sensor. At 2,500 02 voltage should switch rapidly from .200 to .800. On a scope the patern looks like saw teeth. Release throttle and watch 02. It should drop below .200 for a moment during decel fuel cutoff then come back up and continue cycling. The 02 sensor will continue to read normally for several seconds befor it cools back down. The system may go open loop at idle. Thats not unusual and is not a sign of trouble. However, if during testing the O2 voltage tends to hang high or low or cycles slowly it may be a bad O2 sensor. Watch for it to stick high or low as this is a sign of either a lean or rich condition. I suspect you have an issue with either your 02 or MAP.

 

hmm ok thanks for your insight aswell i will look into it with a scal tool, the o2 sensor was replaced 4 months ago and it int change anything, an i replace the map sensor with another from a working car it didnt change anything. maybe they were bad i hear about new o2 sensors going bad out of the box. is there away to test to see if thats the problem with a scan tool i do have a multimeter

 

map sensor was replaced with a brand new replacement and it still does the same thing, also now the car is taking alot longer to start

 

anymore ideas ?

 

Sorry I took so long getting back to you. The O2 test I referred to above should reveal any issues. One quick way to test O2 if in doubt is to simply disconnect it then start and run the engine. This will force the ECM into MEMCAL and it will ignore the O2 sensor. If everything else is okay, the engine should run reasonably well.

As I stated above, the most common cause of surging idle is lean condition. The purpose of the O2 test I detailed for you is to be sure the system is in closed loop, then let it idle and see if the O2 reads lean. You should also look at block learn and integrator on data. They should both hang around 128. Higher numbers mean the engine is running lean.

Did I mention that idle surge can also be caused by the idle air control solenoid(IAC). If integrator and block learn look okay, try unplugging the IAC. If the engine idles okay, the IAC is probably bad.

 

no worries on the timeline I appricate the help im just trying to get this junk running,
I did i compression just for shts and giggles and every cylinder was under 110 one was 95 and then 100 and then one was 110

 

Pour 2 tablespoons of oil in a spark plug hole and retest that cylinder. If compression improves dramatically, its rings and you want to check a few this way to verify. If it doesnt improve with oil, and I have a sense it wont, then you probably have a bad timing chain that has jumped teeth.

A quick test for timing chain slack is to run the engine with a timing light connected. Snap and release the throttle a few times while observing the timing marks. A healthy motor will advance and retard smoothly. A loose timing chain will cause timing to flutter erratically, especially on return to idle from a quick rev. Watch for any sign of this as you snap and release throttle.

The next step is to remove the dist cap. Using a breaker handle and 5/8" socket, turn the crank back and forth while observing the dist rotor. The rotor should move with any movement of the crank. A few degrees of lash is acceptable, however if lash exceeds 5 degrees, you probably need to remove the timing cover to inspect timing chain.

A quick indicator also is to note timing. Has it changed from the last time you set it?

 

it does flutter a little i know from when i set timing So all this can be caused by the timing chain the way the car acts how it surge while i drive, its runs lean, and the slight miss?

 

could that be why i can not get the car to idle right while im setting the iac the car surges way to much when i try and set it.

 

Loss of valve timing will cause volumetric efficiency to drop way off. Base fuel map is calculated base on assumed VE for any given engine. The timing chain jumping throws off valve timing. Your ECM doesnt know what to do when VE goes away.

 

I just thought of something this morning, did you check compression at WOT? Its important that you have the throttle wide open when cranking for this test, with ignition disabled of course. I assumed that you had done this. If not, your compression numbers may not mean anything.

 

im not sure if i did or not damn!! i prolly didnt I will do it again and see if the numbers are correct.

 

Cool. Just try one hole. If its different, then redo the rest. Let me know what you find out.

 

Why are you using only 19lb injectors on a 350 motor? I thought stock was 22 lb/hr.

 

It's a 305 . I just wanted to figure out what the problem was before I swapped in my 350

 

Hey man, check your CTS. Coolant temp sensor.